Nighttime home blood pressure lowering effect of esaxerenone in patients with uncontrolled nocturnal hypertension: the EARLY-NH study.

There is limited evidence on the blood pressure (BP)-lowering effect of esaxerenone on home BP, including nighttime BP. Using two newly developed nocturnal home BP monitoring devices (brachial and wrist), this multicenter, open-label, prospective study investigated the nighttime home BP-lowering effect of esaxerenone in patients with uncontrolled nocturnal hypertension being treated with an angiotensin receptor blocker (ARB) or calcium-channel blocker (CCB). In total, 101 patients were enrolled. During the 12-week study period, change in nighttime home systolic/diastolic BP from baseline to end of treatment measured by the brachial device was -12.9/-5.4 mmHg in the total population and -16.2/-6.6 and -10.0/-4.4 mmHg in the ARB and CCB subcohorts, respectively (all p < 0.001). For the wrist device, the change was -11.7/-5.4 mmHg in the total population and -14.6/-6.2 and -8.3/-4.5 mmHg in each subcohort, respectively (all p < 0.001). Similar significant reductions were shown for morning and bedtime home BP and office BP. Urinary albumin-to-creatinine ratio, N-terminal pro-brain natriuretic peptide, and cardio-ankle vascular index improved in the total population and each subcohort. Incidences of treatment-emergent adverse events (TEAEs) and drug-related TEAEs were 38.6% and 16.8%, respectively; most were mild or moderate. The most frequent drug-related TEAEs were associated with serum potassium elevation (hyperkalemia, 9.9%; blood potassium increased, 3.0%); however, no new safety concerns were raised. Esaxerenone was effective in lowering nighttime home BP as well as morning and bedtime home BP and office BP, safe, and showed organ-protective effects in patients with uncontrolled nocturnal hypertension. Caution is warranted regarding elevated serum potassium levels. This study investigated the effect of esaxerenone on nighttime home BP and organ damage (UACR and NT-proBNP) in patients with uncontrolled nocturnal hypertension despite treatment with an ARB or CCB. Our results show that safe 24-h BP control and organ protection are possible with esaxerenone.

Sleep duration and food intake in people with type 2 diabetes mellitus and factors affecting confectionery intake.

AIMS/INTRODUCTION: We carried out a cross-sectional study of people with type 2 diabetes mellitus to elucidate the association between sleep duration and food intake. MATERIALS AND METHODS: Overall, 2,887 participants with type 2 diabetes mellitus (mean age 63.0 years; 61.1% men; mean glycated hemoglobin level 7.5%) were included in this study. The participants' self-reported dietary habits and sleep duration were evaluated using a brief self-administered dietary history questionnaire and Pittsburgh Sleep Quality Index, respectively. The participants were categorized into the following four groups based on sleep duration: <6, 6-6.9, 7-7.9 (reference) and ≥8 h. RESULTS: No significant differences were observed between the groups regarding energy intake (kcal/day), absolute intake (g/day) or relative intake (% energy) of carbohydrates, total fat, proteins and fibers. However, confectionery intake was higher in the <6 h group and lower in the ≥8 h group than in the reference group after adjustment for confounding factors. In multivariate analysis, sleep durations <6 h and ≥8 h significantly correlated with increased (95% confidence interval 0.55 to 3.6; P = 0.0078) and decreased (95% confidence interval -4.0 to -0.32; P = 0.021) confectionery intake, respectively. Confectionery intake was positively correlated with female sex, glycated hemoglobin level and dyslipidemia, whereas it was negatively correlated with alcohol consumption and current smoking status. CONCLUSIONS: Short sleep duration is associated with high confectionery intake in people with type 2 diabetes mellitus; this might disturb their glycemic control. Therefore, short sleepers with type 2 diabetes mellitus could improve their glycemic control by avoiding confectionery intake and maintaining adequate sleep duration.

Multinational Observational Study to Understand Insulin Treatment Intensification: Japanese Subgroup Analysis of the MOSAIc Study.

INTRODUCTION: MOSAIc was a multinational, non-interventional, prospective, observational cohort study designed to provide an understanding of the specific challenges associated with intensification of initial insulin therapy in patients with type 2 diabetes mellitus (T2DM). We present a sub-analysis of Japanese patients from MOSAIc, with data analyzed longitudinally over 2 years, to provide insight on how T2DM treatment is intensified. METHODS: Japanese patients with T2DM receiving any insulin therapy for at least 3 months were eligible for study inclusion. Baseline and clinical data were collected during an initial baseline visit and during four subsequent prospective visit windows (within ± 3 months) at 6, 12, 18, and 24 months. Treatment intensification was defined as addition of new insulin, increase in insulin dosage (1-unit change or 10% compared with the previous visit), increase in insulin injection frequency, and/or addition of non-insulin antihyperglycemic agents. RESULTS: Of 116 Japanese patients who completed the study, 50.0% (n = 58) received treatment intensification. Baseline characteristics of patients with treatment intensification included a longer duration of diabetes, higher incidence of baseline microvascular complications, and higher HbA1c compared to those without intensification. There was no significant difference in HbA1c change from baseline between the two groups at any post-baseline visit. Insulin intensification accounted for 61.2% of treatment changes, with non-insulin-related intensification accounting for 36.2% of treatment changes. An increase in insulin dose was the most frequent treatment change (51.7%), followed by the addition of new insulin (22.4%), and an increase in insulin injection frequency (6.9%). CONCLUSION: Real-world data from Japanese patients with T2DM who received treatment intensification showed that an increase in insulin dose and the addition of new insulin were the most frequent treatment intensification methods. HbA1c was maintained through 2 years of treatment. TRIAL REGISTRATION: NCT01400971, ClinicalTrials.gov.

A cross-sectional study of the relationship between quality of life and sleep quality in Japanese patients with type 1 diabetes mellitus.

This study aimed to reveal the relationship between quality of life (QOL) and sleep quality in patients with type 1 diabetes mellitus (T1DM). Overall, 202 patients with T1DM were registered in our study, and 192 were eligible for analysis. Baseline characteristics and laboratory values were determined. Patients completed the Japanese versions of the Pittsburgh Sleep Quality Index (PSQI) and Diabetes Therapy-Related QOL (DTR-QOL) questionnaires. We investigated the relationship between the global PSQI and DTR-QOL total scores by using linear regression analysis. In univariate regression analysis, DTR-QOL total scores were associated with body mass index, alcohol consumption, hypertension, hemoglobin A1c (HbA1c), and global PSQI score (all p-value <0.05) but not with sleep duration. When the association between PSQI subscales and DTR-QOL total scores was examined, DTR-QOL total scores were significantly related to subjective sleep quality and daytime dysfunction. In a multivariate regression analysis, the global PSQI score was negatively related to DTR-QOL total scores. Patients with an HbA1c concentration ≥8.0% had significantly lower DTR-QOL total scores. We revealed a relationship between QOL and sleep quality in T1DM patients and showed that the relationship between QOL and PSQI subscales in T1DM patients may be different from that in patients with type 2 diabetes mellitus. Assessing and managing sleep quality may be necessary for patients with diabetes to improve QOL.

Effects of 1-year treatment with canagliflozin on body composition and total body water in patients with type 2 diabetes.

AIM: To characterize the long-term changes in body composition associated with sodium-glucose cotransporter-2 (SGLT2) inhibitors. MATERIALS AND METHODS: In this multicentre, single-arm, open-label study, 107 patients with type 2 diabetes were treated with canagliflozin 100 mg, as add-on therapy, for 12 months. Body composition was measured with a body composition analyser (T-SCAN PLUS) using the impedance method to prospectively analyse changes in body components, including percentage of body fat, body fat mass, total body water, muscle mass and mineral mass. Estimated plasma volume (PV) was calculated using the Kaplan formula. RESULTS: Body weight showed a significant decrease from 1 month to 12 months of treatment with canagliflozin, with a higher rate of decrease in body fat in body composition. A significant decrease in mineral mass was also observed, but its rate was low. Following treatment with canagliflozin, changes in total body water did not affect intracellular water, and a significant decrease in extracellular water, including plasma components, was observed early and was sustained up to 12 months. Protein mass, a component of muscle mass, was not affected, with only a slight decrease in water volume observed. CONCLUSIONS: Canagliflozin decreased extracellular fluid and PV in addition to decreasing fat in the body via calorie loss resulting from urinary glucose excretion. This study suggested that SGLT2 inhibitors might reduce body weight by regulating fat mass or water distribution in the body and might have cardiac and renal protective effects by resetting the homeostasis of fluid balance.

Effects of ipragliflozin on the development and progression of kidney disease in patients with type 2 diabetes: An analysis from a multicenter prospective intervention study.

AIMS/INTRODUCTION: Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. METHODS: This was an investigator-initiated multicenter prospective intervention study in which ipragliflozin (50 mg) was administered once daily, and glycemic control, estimated glomerular filtration rate (eGFR) and adverse events were evaluated until 104 weeks after starting research. RESULTS: There were 407 patients analyzed. In the eGFR ≥90 group and eGFR ≥60 to <90 group, eGFR had significantly decreased compared with baseline at all time points from 4 to 104 weeks. There were significant increases in the eGFR ≥45 to <60 groups compared with baseline at 36 weeks (2.3 ± 1.0) and 52 weeks (2.6 ± 1.2). Comparison between the eGFR <60, urine albumin-to-creatinine ratio >300 group and the eGFR <60, urine albumin-to-creatinine ratio <300 group showed a greater reduction in eGFR in the former (-5.4 ± 2.4 vs 3.3 ± 1.1) at 12 weeks and was maintained to 104 weeks. In any group, eGFR did not significantly decrease until 104 weeks compared with 4 weeks. The urine albumin-to-creatinine ratio after 52 weeks and after 104 weeks was significantly decreased compared with baseline in the eGFR ≥90 group. CONCLUSIONS: Ipragliflozin lowers eGFR and corrects hyperfiltration in patients with high eGFR (eGFR ≥60). In patients with low eGFR (eGFR ≥30 to <60), ipragliflozin has the possibility of increasing eGFR and exerting a renoprotective effect.

Canagliflozin Increases Calorie Intake in Type 2 Diabetes Without Changing the Energy Ratio of the Three Macronutrients: CANA-K Study.

Background: Sodium/glucose cotransporter-2 (SGLT2) inhibitors improve glycemic control and reduce body weight by increasing glycosuria. Although a compensatory increase of food intake has been reported, the long-term effect of SGLT2 inhibitors on food intake remains unclear. This study investigated the influence of canagliflozin on calorie and nutrient intake over 1 year. Materials and Methods: Patients with type 2 diabetes (n = 107) were enrolled and followed prospectively while receiving canagliflozin at 100 mg/day for 12 months. Intake of nutrients was investigated by using the food frequency questionnaire. Hemoglobin A1c, body weight, and satisfaction with diabetes treatment (assessed by the Diabetes Treatment Satisfaction Questionnaire: DTSQ) were also investigated. Results: The baseline total energy intake was 1723 ± 525 kcal/day and it showed a persistent increase during treatment with canagliflozin, being 132 kcal higher at 6 months (P = 0.0058) and 113 kcal higher at 12 months (P = 0.0516). Intake of all three macronutrients (carbohydrate, protein, and fat) was significantly increased after 6 months of canagliflozin treatment (P = 0.0129, P = 0.0160, and P = 0.0314, respectively), but their ratio was unchanged. The DTSQ score improved significantly and both hemoglobin A1c and body weight showed a significant decrease throughout treatment (all P < 0.0001). Conclusions: After patients with type 2 diabetes commenced canagliflozin, their calorie intake increased without changing the ratio of the three macronutrients. Despite elevation of the calorie intake, glycemic control improved and weight loss was achieved. Satisfaction with treatment of diabetes also increased.

Dietary survey in Japanese patients with type 2 diabetes and the influence of dietary carbohydrate on glycated hemoglobin: The Sleep and Food Registry in Kanagawa study.

AIMS/INTRODUCTION: The present study investigated the relationship between the macronutrient energy ratio, dietary carbohydrate and glycated hemoglobin levels in Japanese patients with type 2 diabetes, to generate a potential optimal dietary intake of macronutrients for such patients. MATERIALS AND METHODS: In total, 3,032 patients participating in the Sleep and Food Registry in Kanagawa study were evaluated. Their diets were assessed for macronutrient content through a brief self-administered dietary history questionnaire. Relevant biochemical assays were carried out. RESULTS: The mean energy intake (±standard deviation) was 1,711 ± 645 kcal/day. The proportion of energy supplied by protein, fat and carbohydrate were 16.3, 26.8 and 52.3%, respectively. Total fiber intake was 12.6 ± 5.7 g/day. The high glycated hemoglobin (HbA1c) group (HbA1c >8%) had significantly lower protein and higher carbohydrate intake than the low HbA1c group (HbA1c <6.5%). Higher HbA1c levels were positively correlated with unfavorable metabolic factors, including elevated body mass index and excess carbohydrate intake, and negatively correlated with age, protein intake and fiber intake. Multiple regression analysis showed a significant association between HbA1c and carbohydrate intake after adjusting for sex, age and body mass index (0.104, P < 0.0001). Additionally, patients within the uppermost tertile for the percentage of total energy intake from carbohydrate (>60%) were most likely to have high HbA1c levels. HbA1c was significantly correlated with carbohydrate (%E) in all age groups and in patients taking one or two antidiabetic drugs. CONCLUSIONS: The dietary carbohydrate:energy ratio has a positive correlation with HbA1c, suggesting that avoiding excessive carbohydrate intake (>60%) might help foster glycemic control.

Effectiveness of Ipragliflozin for Reducing Hemoglobin A1c in Patients With a Shorter Type 2 Diabetes Duration: Interim Report of the ASSIGN-K Study.

BACKGROUND: Ipragliflozin is a selective sodium glucose co-transporter 2 inhibitor. The ASSIGN-K study is investigating the efficacy and safety of ipragliflozin for type 2 diabetes mellitus (T2DM) in the real-world clinical setting. METHODS: Japanese T2DM patients with inadequate glycemic control despite diet and exercise with/without pharmacotherapy were enrolled in an investigator-driven, multicenter, prospective, observational study examining the efficacy and safety of ipragliflozin treatment (50 mg/day for 52 weeks). We performed interim analysis after 24 weeks. RESULTS: In 367 patients completing 24-week ipragliflozin therapy, hemoglobin A1c (HbA1c) decreased significantly from 8.07% at baseline to 7.26% in week 24 (P < 0.001). The change in HbA1c from treatment initiation to week 24 was -0.88% in patients < 65 years old versus -0.55% in those ≥ 65 years and -0.92% in men versus -0.70% in women (all P < 0.001). When baseline HbA1c was < 7%, 7% to < 8%, and ≥ 8%, the change was -0.18%, -0.45%, and -1.48%, respectively (P = 0.5352, P < 0.001, and P < 0.001, respectively). When baseline body mass index (BMI) was < 25, 25 to < 30, and ≥ 30, the change was -1.05%, -0.65%, and -0.87%, respectively (all P < 0.001). Multiple regression analysis showed that HbA1c decreased more in patients with a higher baseline HbA1c or shorter duration of diabetes. An HbA1c < 7% was achieved in 33.3% of the patients, and their baseline HbA1c was significantly lower than that of patients failing to achieve it (P < 0.001). Adverse events (AEs) occurred in 106/451 patients (23.5%), including 29.1% of patients aged 65 or older. Common AEs were vulvovaginal candidiasis (3.1%) and genital pruritus (1.8%). Serious AEs included urinary tract infection, unstable angina, and ketosis, which occurred in patients who did not suspend medication during acute illness. CONCLUSIONS: Ipragliflozin significantly improved HbA1c in T2DM patients with inadequate glycemic control. Improvement in HbA1c was significant irrespective of age, sex, baseline HbA1c, or BMI, but efficacy was greater with a higher baseline HbA1c and shorter duration of diabetes. For safe continuation of treatment, patients should be advised to suspend medication during acute illness.

Ipragliflozin Improves Glycemic Control and Decreases Body Fat in Patients With Type 2 Diabetes Mellitus.

BACKGROUND: Ipragliflozin, a sodium-glucose transporter 2 inhibitor, was administered to patients with type 2 diabetes mellitus for 24 weeks to evaluate its effect on glycemic control and body composition. METHODS: This was an investigator-initiated multicenter prospective intervention study in which ipragliflozin (50 mg) was administered once daily and glycemic control, blood pressure, body weight (BW), body composition (measured by a biological impedance method), the lipid profile, and adverse events were evaluated after 4, 12, and 24 weeks of treatment. RESULTS: Efficacy and safety up to 24 weeks of ipragliflozin therapy were analyzed in 367 patients and 451 patients, respectively. Hemoglobin A1c decreased significantly from 8.07% at the start of ipragliflozin therapy to 7.26% in week 24 (P < 0.001). Fasting and postprandial blood glucose levels were significantly reduced by ipragliflozin. In week 24, there were significant decreases from baseline in BW (-2.6 kg), waist circumference (-2.9 cm), and body fat mass (-1.9 kg) (P < 0.001). The body water mass and mineral mass were decreased significantly by 0.5 and by 0.1 kg, respectively (P < 0.001), whereas the protein mass did not change significantly. Intracellular water mass did not change significantly, whereas extracellular water mass showed a significant decrease of 0.5 kg (P < 0.001). Muscle mass did not change in the upper and lower limbs, but that of the trunk decreased significantly (P < 0.001). There was a significant decrease in the fasting triglyceride level and a significant increase in fasting high-density lipoprotein cholesterol level, while low-density lipoprotein cholesterol was unchanged. Adverse events occurred in 23.5% of the patients, with a high frequency of genital infections, such as vulvovaginal candidiasis (3.1%) and genital pruritus (1.8%). Adverse drug reactions were noted in 13.7% of the patients. CONCLUSIONS: Administration of ipragliflozin for 24 weeks improved glycemic control and decreased BW. Reduction of body fat accounted for more than 70% of the total weight loss and reduction of extracellular water accounted for about 20%.

Cross-National Variation in Glycemic Control and Diabetes-Related Distress Among East Asian Patients Using Insulin: Results from the MOSAIc Study.

INTRODUCTION: Guidelines recommend insulin progression for patients with type 2 diabetes (T2D) with inadequate glycemic control. The Multinational Observational Study Assessing Insulin use (MOSAIc [ClinicalTrials.gov identifier, NCT01400971]) study is a 2-year observational study, investigating factors that influence insulin progression in T2D patients. In this first of two reports, we describe baseline clinical and psychosocial characteristics of Chinese, Japanese, and South Korean patients who participated in MOSAIc. Insulin treatment, factors affecting progression, and outcomes will be reported separately. METHODS: Patients with T2D using insulin for ≥3 months were eligible. Baseline demographic, clinical, and psychosocial data were collected from patients. Quality of life instruments, including the Diabetes Distress Scale (DDS), were used to assess patient's concerns about disease management, support, and emotional burden. The association between the DDS and the selected covariates was also assessed. RESULTS: A total of 373 patients in China, 157 in Japan, and 141 in South Korea were enrolled from July 2011 to July 2013. Mean ± standard deviation duration (years) of T2D differed across countries (China 11.4 ± 7.5; Japan 13.8 ± 8.7; South Korea 15.7 ± 8.8; P < 0.0001). Japanese patients used more noninsulin anti-hyperglycemic agents than did Chinese or South Korean patients (P < 0.0001). Exclusive use of basal insulin was most common in Japan and South Korea compared with China, whereas approximately 66.8% of Chinese patients used mixed insulin. Covariates associated with the DDS were younger age [P = 0.044 (Japan)], higher incidence of monthly hypoglycemia [P = 0.036 [China]; P = 0.021 (South Korea)], and male gender [P = 0.037 (South Korea)]. CONCLUSIONS: There were significant differences amongst East Asian patients with T2D treated with insulin, including in quality of life scores. Results from the MOSAIc longitudinal analyses will further investigate trends of insulin intensification and barriers to insulin progression. FUNDING: Eli Lilly and Company.

Factors Influencing Changes in Hemoglobin A1c and Body Weight During Treatment of Type 2 Diabetes With Ipragliflozin: Interim Analysis of the ASSIGN-K Study.

BACKGROUND: Ipragliflozin is a selective sodium glucose co-transporter 2 (SGLT2) inhibitor that blocks glucose reabsorption in the proximal tubules. SGLT2 inhibitors are expected to be effective in patients with insulin resistance and obesity, but it is important to select treatment according to patient background factors that minimizes the risk of adverse events. There have been a limited number of investigations into the relationship between the clinical efficacy (reducing hemoglobin A1c (HbA1c) and body weight (BW)) or safety of SGLT2 inhibitors and patient characteristics. METHODS: ASSIGN-K is an investigator-initiated, multicenter, prospective observational study examining the efficacy and safety of ipragliflozin (50 - 100 mg/day for 52 weeks) in Japanese patients with type 2 diabetes mellitus (T2DM) who had inadequate glycemic control with HbA1c ≥ 6.0% (National Glycohemoglobin Standardization Program) despite diet and exercise therapy or diet and exercise plus antidiabetic drug therapy. We conducted an interim analysis of the relationship between changes in HbA1c or BW and characteristics in patients who had been on treatment for more than 12 weeks. RESULTS: In 257 patients completing 12 weeks of treatment, HbA1c decreased significantly from 8.23% to 7.55% (-0.68%, P < 0.01). The change in HbA1c after 12 weeks was -0.17%, -0.33%, and -1.16% when baseline HbA1c was < 7%, 7% to < 8%, and ≥ 8%, respectively (P < 0.05, P < 0.01, and P < 0.01, respectively), and -1.30%, -0.62%, and -0.62% when baseline body mass index (BMI) was < 25, 25 to < 30, and ≥ 30, respectively (all P < 0.01). Stratified analysis showed that age, gender, or BMI did not have a significant influence on the improvement in HbA1c. Multiple regression analysis showed that reduction in HbA1c was greater as baseline HbA1c increased and the duration of diabetes decreased. A higher baseline HbA1c was associated with less weight loss. CONCLUSIONS: Ipragliflozin significantly improved HbA1c in patients with T2DM. HbA1c improved more when baseline HbA1c was higher and the duration of diabetes was shorter, suggesting that current treatment policies for diabetes could be re-examined.

Correction: Efficacy and Safety of Ipragliflozin in Japanese Patients With Type 2 Diabetes: Interim Outcome of the ASSIGN-K Study.

[This corrects the article DOI: 10.14740/jocmr2417w.].

Efficacy and Safety of Ipragliflozin in Japanese Patients With Type 2 Diabetes: Interim Outcome of the ASSIGN-K Study.

BACKGROUND: Ipragliflozin is a sodium-glucose co-transporter 2 inhibitor that can improve glycemic control and reduce body weight and blood pressure in patients with type 2 diabetes mellitus (T2DM). We evaluated the efficacy and safety of ipragliflozin in the real-world clinical setting, with a focus on the changes of body composition up to 3 months of treatment. METHODS: This was a prospective multicenter interventional trial. We investigated changes of the blood pressure, body composition, blood glucose, hemoglobin A1c (HbA1c), ketone bodies, lipids, and insulin after treatment with ipragliflozin (50 - 100 mg/day) for 12 weeks in Japanese patients with T2DM who showed poor glycemic control despite receiving diet and exercise therapy with or without oral antidiabetic drugs for more than 12 weeks. RESULTS: Two hundred and fifty-seven subjects were included in the efficacy analysis up to 12 weeks of treatment and 301 subjects were included in the safety analysis. From baseline to 12 weeks, HbA1c showed a change of -0.68% (95% confidence interval (CI): -0.83, -0.53) and fasting blood glucose showed a change of -23.9 mg/dL (95% CI: -30.5, -17.2), with both parameters displaying a significant reduction (P < 0.001). The difference of body weight from baseline was -1.82 kg (95% CI: -2.14, -1.50), and it also showed significant reduction (P < 0.001). Analysis of body composition revealed that body fat changed by -1.46 kg (95% CI: -1.79, -1.14, P < 0.001) and body water changed by -0.37 kg (95% CI: -0.60, -0.14, P < 0.01). Laboratory tests demonstrated improvement of liver function and the lipid profile. Adverse events (AEs) occurred in 22.6% of the subjects, with frequent events being vulvovaginal candidiasis in 2.7% and cystitis in 2.0%. Serious AEs occurred in three subjects. CONCLUSIONS: In patients with T2DM, ipragliflozin improved glycemic control after 1 month of treatment and caused weight loss by reducing body fat more than body water.

IRE-1/XBP-1 pathway of the unfolded protein response is required for properly localizing neuronal UNC-6/Netrin for axon guidance in C. elegans.

During developing nervous system, neurons project axons to their targets precisely. In this process, axon guidance molecules provide positional information to the axons. Therefore, the spatially and temporally controlled localization of the axon guidance molecules is required for the proper structure formation of the complex nervous system. In C. elegans, UNC-6/Netrin is a secreted protein that elicits both attractive and repulsive response in axon guidance. UNC-6/Netrin secreted from ventral cells may establish a concentration gradient from the ventral to the dorsal side of the animal, thus providing dorso-ventral positional information. However, the mechanisms specifying positional information of UNC-6/Netrin are largely unknown. Here, we show that the ire-1/xbp-1 pathway of the unfolded protein response (UPR) is required for axonal distribution of UNC-6/Netrin in the ventral neurons. In addition, the ire-1/xbp-1 pathway is also required for dorso-ventral axon guidance mediated by UNC-6/Netrin. Our results suggest that the ire-1/xbp-1 pathway of the UPR is crucial for establishing positional information of UNC-6/Netrin. We propose that the proper secretion of UNC-6/Netrin from the ventral neurons requires the activity of IRE-1.

Localization mechanisms of the axon guidance molecule UNC-6/Netrin and its receptors, UNC-5 and UNC-40, in Caenorhabditis elegans.

Netrin is an evolutionarily conserved, secretory axon guidance molecule. Netrin's receptors, UNC-5 and UNC-40/DCC, are single trans-membrane proteins with immunoglobulin domains at their extra-cellular regions. Netrin is thought to provide its positional information by establishing a concentration gradient. UNC-5 and UNC-40 act at growth cones, which are specialized axonal tip structures that are generally located at a long distance from the neural cell body. Thus, the proper localization of both Netrin and its receptors is critical for their function. This review addresses the localization mechanisms of UNC-6/Netrin and its receptors in Caenorhabditis elegans, focusing on our recent reports. These findings include novel insights on cytoplasmic proteins that function upstream of the receptors.

A seven-transmembrane receptor that mediates avoidance response to dihydrocaffeic acid, a water-soluble repellent in Caenorhabditis elegans.

The ability to detect harmful chemicals rapidly is essential for the survival of all animals. In Caenorhabditis elegans (C. elegans), repellents trigger an avoidance response, causing animals to move away from repellents. Dihydrocaffeic acid (DHCA) is a water-soluble repellent and nonflavonoid catecholic compound that can be found in plant products. Using a Xenopus laevis (X. laevis) oocyte expression system, we identified a candidate dihydrocaffeic acid receptor (DCAR), DCAR-1. DCAR-1 is a novel seven-transmembrane protein that is expressed in the ASH avoidance sensory neurons of C. elegans. dcar-1 mutant animals are defective in avoidance response to DHCA, and cell-specific expression of dcar-1 in the ASH neurons of dcar-1 mutant animals rescued the defect in avoidance response to DHCA. Our findings identify DCAR-1 as the first seven-transmembrane receptor required for avoidance of a water-soluble repellent, DHCA, in C. elegans.

Genes required for cellular UNC-6/netrin localization in Caenorhabditis elegans.

UNC-6/Netrin is an evolutionarily conserved, secretory axon guidance molecule. In Caenorhabditis elegans, UNC-6 provides positional information to the axons of developing neurons, probably by establishing a concentration gradient from the ventral to the dorsal side of the animal. Although the proper localization of UNC-6 is important for accurate neuronal network formation, little is known about how its localization is regulated. Here, to examine the localization mechanism for UNC-6, we generated C. elegans expressing UNC-6 tagged with the fluorescent protein Venus and identified 13 genes, which are involved in the cellular localization of VenusUNC-6. For example, in unc-51, unc-14, and unc-104 mutants, the neurons showed an abnormal accumulation of VenusUNC-6 in the cell body and less than normal level of VenusUNC-6 in the axon. An aberrant accumulation of VenusUNC-6 in muscle cells was seen in unc-18 and unc-68 mutants. unc-51, unc-14, and unc-104 mutants also showed defects in the guidance of dorso-ventral axons, suggesting that the abnormal localization of UNC-6 disturbed the positional information it provides. We propose that these genes regulate the process of UNC-6 secretion: expression, maturation, sorting, transport, or exocytosis. Our findings provide novel insight into the localization mechanism of the axon guidance molecule UNC-6/Netrin.

UNC-6 expression by the vulval precursor cells of Caenorhabditis elegans is required for the complex axon guidance of the HSN neurons.

Netrin is an evolutionarily conserved axon guidance molecule that has both axonal attraction and repulsion activities. In Caenorhabditis elegans, Netrin/UNC-6 is secreted by ventral cells, attracting some axons ventrally and repelling some axons, which extend dorsally. One axon guided by UNC-6 is that of the HSN neuron. The axon guidance process for HSN neurons is complex, consisting of ventral growth, dorsal growth, branching, second ventral growth, fasciculation with ventral nerve cords, and then anterior growth. The vulval precursor cells (VPC) and the PVP and PVQ neurons are required for the HSN axon guidance; however, the molecular mechanisms involved are completely unknown. In this study, we found that the VPC strongly expressed UNC-6 during HSN axon growth. Silencing of UNC-6 expression in only the VPC, using a novel tissue-specific RNAi technique, resulted in abnormal HSN axon guidance. The expression of Netrin/UNC-6 by only the VPC in unc-6 null mutants partially rescued the HSN ventral axon guidance. Furthermore, the expression of Netrin/UNC-6 by the VPC and the ventral nerve cord (VNC) in unc-6 null mutants restored the complex HSN axon guidance. These results suggest that UNC-6 expressed by the VPC and the VNC cooperatively regulates the complex HSN axon guidance.

Differential effects of methamphetamine and cocaine on behavior and extracellular levels of dopamine and 3,4-dihydroxyphenylalanine in the nucleus accumbens of conscious rats.

The central dopamine system plays a prominent role in the effect of psychostimulants such as methamphetamine, cocaine and nicotine. l-3,4-Dihydroxyphenylalanine (DOPA), a precursor of dopamine, has been proposed as a neurotransmitter in the central nervous system. We have studied the effects of these psychostimulants on the release of DOPA and dopamine from the nucleus accumbens shell in conscious rats using in vivo microdialysis. Methamphetamine and cocaine increase the extracellular levels of dopamine. The effect of methamphetamine (1 mg/kg s.c.) on the release of dopamine was almost comparable to that of cocaine (10 mg/kg i.p.). However, methamphetamine increases, but cocaine decreases the extracellular levels of DOPA. In a behavioral study, methamphetamine (1 mg/kg s.c.) induced chewing, walking and sniffing behavior. Cocaine (10 mg/kg i.p.) produces weak effects on these behavioral parameters, when compared to the effects of methamphetamine (1 mg/kg s.c.). The behavioral changes produced by methamphetamine are suppressed by DOPA cyclohexyl ester (30 mg/kg i.p.), a competitive DOPA antagonist. Endogenous DOPA in the nucleus accumbens thus appears to be in involved in the behavioral responses to these psychomotor stimulants.