Patient-reported outcomes for older adults on CamAPS FX closed loop system.

AIMS: Use of the CamAPS FX hybrid closed loop (CL) system is associated with improved time in range and glycated haemoglobin A1c across the age span, but little is known about its effects on patient-reported outcomes (PROs). METHODS: This open-label, randomized, multi-site study compared CamAPS FX to sensor-augmented pump (SAP) in a sample of older adults (≥60 years) with type 1 diabetes (T1D). Thirty-five older adults completed PROs surveys at the start of the study and after each period of 16 weeks using either CL or SAP. At the end of the study, 19 participated in interviews about their experiences with CL. RESULTS: Results examining the 16 weeks of CL use showed that the overall Diabetes Distress Scale score and two subscales (powerlessness and physician distress) improved significantly along with trust on the Glucose Monitoring Satisfaction Survey. User experience interview responses were consistent in noting benefits of 'improved glycaemic control' and 'worrying less about diabetes'. CONCLUSION: In this sample of older adults with T1D who have previously shown glycaemic benefit, there are indicators of improved PROs and subjective user experience benefits.

Delivering evidence-based interventions for type 1 diabetes in the virtual world - A review of UK practice during the SARS-CoV-2 pandemic.

AIMS: This review considers the impact of the SARS-CoV-2 pandemic on access to interventions for those living with type 1 diabetes and discusses the solutions which have been considered and actioned to ensure ongoing access care. METHODS: We performed a focussed review of the published literature, and the guidelines for changes that have been effected during the pandemic. We also drew from expert recommendations and information about local practice changes for areas where formal data have not been published. RESULTS: Evidence based interventions which support the achievement of improved glucose levels and/or reduction in hypoglycaemia include group structured education to support self-management, insulin pump therapy and continuous glucose monitoring. The SARS-CoV-2 pandemic had impacted the ability of diabetes services to deliver these intervention. Multiple adaptations have been put in place - transition to online delivery of education and care, and usage of diabetes technology. CONCLUSIONS: Although various adaptations have been made during the pandemic that have positively influenced uptake of services, there are many areas of delivery that need immediate improvement in the UK. We recommend a proactive approach in recognising the digital divide and inequity in distribution of these changes and we recommend introducing measures to reduce them.

Bolusing frequency and amount impacts glucose control during hybrid closed-loop.

AIM: To compare bolus insulin delivery patterns during closed-loop home studies in adults with suboptimally [HbA1c 58-86 mmol/mol (7.5%-10%)] and well-controlled [58 mmol/mol (< 7.5%)] Type 1 diabetes. METHODS: Retrospective analysis of daytime and night-time insulin delivery during home use of closed-loop over 4 weeks. Daytime and night-time controller effort, defined as amount of insulin delivered by closed-loop relative to usual basal insulin delivery, and daytime bolus effort, defined as total bolus insulin delivery relative to total daytime insulin delivery were compared between both cohorts. Correlation analysis was performed between individual bolus behaviour (bolus effort and frequency) and daytime controller efforts, and proportion of time spent within and below sensor glucose target range. RESULTS: Individuals with suboptimally controlled Type 1 diabetes had significantly lower bolus effort (P = 0.038) and daily bolus frequency (P < 0.001) compared with those with well-controlled diabetes. Controller effort during both daytime (P = 0.007) and night-time (P = 0.005) were significantly higher for those with suboptimally controlled Type 1 diabetes. Time when glucose was within the target range (3.9-10.0 mmol/L) during daytime correlated positively with bolus effort (r = 0.37, P = 0.016) and bolus frequency (r = 0.33, P = 0.037). Time when glucose was below the target range during daytime was comparable in both groups (P = 0.36), and did not correlate significantly with bolus effort (r = 0.28, P = 0.066) or bolus frequency (r = -0.21, P = 0.19). CONCLUSION: More frequent bolusing and higher proportion of insulin delivered as bolus during hybrid closed-loop use correlated positively with time glucose was in target range. This emphasises the need for user input and educational support to benefit from this novel therapeutic modality.

Home Use of an Artificial Beta Cell in Type 1 Diabetes.

BACKGROUND: The feasibility, safety, and efficacy of prolonged use of an artificial beta cell (closed-loop insulin-delivery system) in the home setting have not been established. METHODS: In two multicenter, crossover, randomized, controlled studies conducted under free-living home conditions, we compared closed-loop insulin delivery with sensor-augmented pump therapy in 58 patients with type 1 diabetes. The closed-loop system was used day and night by 33 adults and overnight by 25 children and adolescents. Participants used the closed-loop system for a 12-week period and sensor-augmented pump therapy (control) for a similar period. The primary end point was the proportion of time that the glucose level was between 70 mg and 180 mg per deciliter for adults and between 70 mg and 145 mg per deciliter for children and adolescents. RESULTS: Among adults, the proportion of time that the glucose level was in the target range was 11.0 percentage points (95% confidence interval [CI], 8.1 to 13.8) greater with the use of the closed-loop system day and night than with control therapy (P<0.001). The mean glucose level was lower during the closed-loop phase than during the control phase (difference, -11 mg per deciliter; 95% CI, -17 to -6; P<0.001), as were the area under the curve for the period when the glucose level was less than 63 mg per deciliter (39% lower; 95% CI, 24 to 51; P<0.001) and the mean glycated hemoglobin level (difference, -0.3%; 95% CI, -0.5 to -0.1; P=0.002). Among children and adolescents, the proportion of time with the nighttime glucose level in the target range was higher during the closed-loop phase than during the control phase (by 24.7 percentage points; 95% CI, 20.6 to 28.7; P<0.001), and the mean nighttime glucose level was lower (difference, -29 mg per deciliter; 95% CI, -39 to -20; P<0.001). The area under the curve for the period in which the day-and-night glucose levels were less than 63 mg per deciliter was lower by 42% (95% CI, 4 to 65; P=0.03). Three severe hypoglycemic episodes occurred during the closed-loop phase when the closed-loop system was not in use. CONCLUSIONS: Among patients with type 1 diabetes, 12-week use of a closed-loop system, as compared with sensor-augmented pump therapy, improved glucose control, reduced hypoglycemia, and, in adults, resulted in a lower glycated hemoglobin level. (Funded by the JDRF and others; AP@home04 and APCam08 ClinicalTrials.gov numbers, NCT01961622 and NCT01778348.).

Psychosocial aspects of closed- and open-loop insulin delivery: closing the loop in adults with Type 1 diabetes in the home setting.

AIMS: To explore the psychosocial experiences of closed-loop technology and to compare ratings of closed- and open-loop technology for adults with Type 1 diabetes taking part in a randomized crossover study. METHODS: Adults (aged > 18 years) on insulin pump therapy were recruited to receive a first phase of either real-time continuous glucose monitoring with overnight closed-loop or real-time continuous glucose monitoring alone (open-loop) followed by a second phase of the alternative treatment in random order, at home for 4 weeks, unsupervised. Participants were invited to share their views in semi-structured interviews. The impact of the closed-loop technology, positive and negative aspects of living with the device overnight, along with the hopes and anxieties of the participants, were explored. RESULTS: The participants in the trial were 24 adults with a mean (sd) age of 43 (12) years, of whom 54% were men. The mean (range) interview duration was 26 (12-46) min. Content and thematic analysis showed the following key positive themes: improved blood glucose control (n = 16); reassurance/reduced worry (n = 16); improved overnight control leading to improved daily functioning and diabetes control (n = 16); and improved sleep (n = 8). The key negative themes were: technical difficulties (n = 24); intrusiveness of alarms (n = 13); and size of equipment (n = 7). Of the 24 participant, 20 would recommend the closed-loop technology. CONCLUSIONS: Closed-loop therapy has positive effects when it works in freeing participants from the demands of self-management. The downside was technical difficulties, particularly concerning the pump and 'connectivity', which it is hoped will improve. Future research should continue to explore the acceptability of the closed-loop system as a realistic therapy option, taking account of user concerns as new systems are designed. Failure to do this may reduce the eventual utility of new systems.

Unsupervised home use of an overnight closed-loop system over 3-4 weeks: a pooled analysis of randomized controlled studies in adults and adolescents with type 1 diabetes.

AIMS: To compare overnight closed-loop and sensor-augmented pump therapy in patients with type 1 diabetes by combining data collected during free-living unsupervised randomized crossover home studies. METHODS: A total of 40 participants with type 1 diabetes, of whom 24 were adults [mean ± standard deviation (s.d.) age 43 ± 12 years and glycated haemoglobin (HbA1c) 8.0 ± 0.9%] and 16 were adolescents (mean ± s.d. age 15.6 ± 3.6 years and HbA1c 8.1 ± 0.8%), underwent two periods of sensor-augmented pump therapy in the home setting, in combination with or without an overnight closed-loop insulin delivery system that uses a model predictive control algorithm to direct insulin delivery. The order of the two interventions was random; each period lasted 4 weeks in adults and 3 weeks in adolescents. The primary outcome was time during which sensor glucose readings were in the target range of 3.9-8.0 mmol/l. RESULTS: The proportion of time when sensor glucose was in the target range (3.9-8.0 mmol/l) overnight (between 24:00 and 08:00 hours) was 18.5% greater during closed-loop insulin delivery than during sensor-augmented therapy (p < 0.001). Closed-loop therapy significantly reduced mean overnight glucose levels by 0.9 mmol/l (p < 0.001), with no difference in glycaemic variability, as measured by the standard deviation of sensor glucose. Time spent above the target range was reduced (p = 0.001), as was time spent in hypoglycaemia (<3.9 mmol/l; p = 0.014) during closed-loop therapy. Lower mean overnight glucose levels during closed-loop therapy were brought about by increased overnight insulin delivery (p < 0.001) without changes to the total daily delivery (p = 0.84). CONCLUSION: Overnight closed-loop insulin therapy at home in adults and adolescents with type 1 diabetes is feasible, showing improvements in glucose control and reducing the risk of nocturnal hypoglycaemia.

Brain glucose sensing, glucokinase and neural control of metabolism and islet function.

It is increasingly apparent that the brain plays a central role in metabolic homeostasis, including the maintenance of blood glucose. This is achieved by various efferent pathways from the brain to periphery, which help control hepatic glucose flux and perhaps insulin-stimulated insulin secretion. Also, critically important for the brain given its dependence on a constant supply of glucose as a fuel--emergency counter-regulatory responses are triggered by the brain if blood glucose starts to fall. To exert these control functions, the brain needs to detect rapidly and accurately changes in blood glucose. In this review, we summarize some of the mechanisms postulated to play a role in this and examine the potential role of the low-affinity hexokinase, glucokinase, in the brain as a key part of some of this sensing. We also discuss how these processes may become altered in diabetes and related metabolic diseases.

Glucose turnover after replacement of usual therapy by insulin in insulin-naive type 2 diabetes subjects.

CONTEXT: Discontinuation of anti-hyperglycemic oral agents and initiation of insulin is recommended in certain clinical situations for inpatients with type 2 diabetes (T2D). The effects on glucose turnover when these agents are acutely withdrawn are poorly understood and may be of importance when insulin therapy is initiated. OBJECTIVE: Our objective was to investigate alterations in glucose turnover after acute withdrawal of noninsulin therapy. DESIGN AND SETTING: This was a randomized crossover study at a clinical research facility. PARTICIPANTS: Participants included 12 insulin-naive subjects with T2D. METHODS: Subjects attended two 24-hour visits. Standard therapy was discontinued and replaced by closed-loop insulin delivery during the intervention visit. Usual anti-hyperglycemic therapy was continued during the control visit. Systemic glucose appearance (Ra) and glucose disposal (Rd) were measured using a tracer dilution technique with iv [6,6-(2)H2]glucose. RESULTS: Plasma glucose profiles during both visits were comparable (P = .48). Glucose Ra increased during the day (21.4 [19.5, 23.5] vs 18.6 [17.0, 21.6) µmol/kg/min, P = .019) and decreased overnight (9.7 [8.5, 11.4] vs 11.6 [10.3, 12.9] µmol/kg/min, P = .004) when the usual therapy was discontinued and replaced with insulin. Increased daytime glucose Rd (21.2 [19.4, 23.9] vs 18.8 [18.3, 21.7] µmol/kg/min, P = .002) and decreased overnight Rd (10.4 [9.1, 12.0] vs 11.8 [10.7, 13.7] µmol/kg/min, P = .005) were observed when the usual therapy was discontinued, whereas daytime peripheral insulin sensitivity was reduced (47.8 [24.8, 66.1] vs 62.5 [34.8, 75.8] nmol/kg/min per pmol/L, P = .034). CONCLUSION: In T2D, acute discontinuation of anti-hyperglycemic therapy and replacement with insulin increases postprandial Ra and reduces peripheral insulin sensitivity. Insulin dose initiation may need to compensate for these alterations.

Absorption patterns of meals containing complex carbohydrates in type 1 diabetes.

AIMS/HYPOTHESIS: Successful postprandial glycaemia management requires understanding of absorption patterns after meals containing variable complex carbohydrates. We studied eight young participants with type 1 diabetes to investigate a large low-glycaemic-load (LG) meal and another eight participants to investigate a high-glycaemic-load (HG) meal matched for carbohydrates (121 g). METHODS: On Visit 1, participants consumed an evening meal. On follow-up Visit 2, a variable-target glucose clamp was performed to reproduce glucose and insulin levels from Visit 1. Adopting stable-label tracer dilution methodology, we measured endogenous glucose production on Visit 2 and subtracted it from total glucose appearance measured on Visit 1 to obtain meal-attributable glucose appearance. RESULTS: After the LG meal, 25%, 50% and 75% of cumulative glucose appearance was at 88 ± 21, 175 ± 39 and 270 ± 54 min (mean ± SD), whereas glucose from the HG meal appeared significantly faster at 56 ± 12, 100 ± 25 and 153 ± 39 min (p < 0.001 to 0.003), and resulted in a 50% higher peak appearance (p < 0.001). Higher apparent bioavailability by 15% (p = 0.037) was observed after the LG meal. We documented a 20 min deceleration of dietary mixed carbohydrates compared with dietary glucose for the HG meal and a twofold deceleration for the LG meal. CONCLUSIONS/INTERPRETATION: Absorption patterns may be influenced by glycaemic load and/or meal composition, affecting optimum prandial insulin dosing in type 1 diabetes.

Yield Loss in Cereals, Caused by Fusarium culmorum and F. pseudograminearum, Is Related to Fungal DNA in Soil Prior to Planting, Rainfall, and Cereal Type.

In southeastern Australia, Fusarium crown rot, caused by Fusarium culmorum or F. pseudograminearum, is an increasingly important disease of cereals. Because in-crop control options are limited, it is important for growers to know prior to planting which fields are at risk of yield loss from crown rot. Understanding the relationships between crown rot inoculum and yield loss would assist in assessing the risk of yield loss from crown rot in fields prior to planting. Thirty-five data sets from crown rot management experiments conducted in the states of South Australia and Victoria during the years 2005 to 2010 were examined. Relationships between Fusarium spp. DNA concentrations (inoculum) in soil samples taken prior to planting and disease development and grain yield were evaluated in seasons with contrasting seasonal rainfall. F. culmorum and F. pseudograminearum DNA concentrations in soil prior to planting were found to be positively related to crown rot expression (stem browning and whiteheads) and negatively related to grain yield of durum wheat, bread wheat, and barley. Losses from crown rot were greatest when rainfall during September and October (crop maturation) was below the long-term average. Losses from crown rot were greater in durum wheat than bread wheat and least in barley. Yield losses from F. pseudograminearum were similar to yield losses from F. culmorum. Yield loss patterns were consistent across experiments and between states; therefore, it is reasonable to expect that similar relationships will occur over broad geographic areas. This suggests that quantitative polymerase chain reaction technology and soil sampling could be powerful tools for assessing crown rot inoculum concentrations prior to planting and predicting the risk of yield loss from crown rot wherever this disease is an issue.

Somatostatin receptor 5 and cannabinoid receptor 1 activation inhibit secretion of glucose-dependent insulinotropic polypeptide from intestinal K cells in rodents.

AIMS/HYPOTHESIS: Glucose-dependent insulinotropic polypeptide (GIP) is an enteroendocrine hormone that promotes storage of glucose and fat. Its secretion from intestinal K cells is triggered by nutrient ingestion and is modulated by intracellular cAMP. In view of the proadipogenic actions of GIP, this study aimed to identify pathways in K cells that lower cAMP levels and GIP secretion. METHODS: Murine K cells purified by flow cytometry were analysed for expression of G(αi)-coupled receptors by transcriptomic microarrays. Somatostatin and cannabinoid receptor expression was confirmed by quantitative RT-PCR. Hormone secretion in vitro was measured in GLUTag and primary murine intestinal cultures. cAMP was monitored in GLUTag cells using the genetically encoded sensor Epac2-camps. In vivo tolerance tests were performed in cannulated rats. RESULTS: Purified murine K cells expressed high mRNA levels for somatostatin receptors (Sstrs) Sstr2, Sstr3 and Sstr5, and cannabinoid receptor type 1 (Cnr1, CB1). Somatostatin inhibited GIP and glucagon-like peptide-1 (GLP-1) secretion from primary small intestinal cultures, in part through SSTR5, and reduced cAMP generation in GLUTag cells. Although the CB1 agonist methanandamide (mAEA) inhibited GIP secretion, no significant effect was observed on GLP-1 secretion from primary cultures. In cannulated rats, treatment with mAEA prior to an oral glucose tolerance test suppressed plasma GIP but not GLP-1 levels, whereas the CB1 antagonist AM251 elevated basal GIP concentrations. CONCLUSIONS/INTERPRETATION: GIP release is inhibited by somatostatin and CB1 agonists. The differential effects of CB1 ligands on GIP and GLP-1 release may provide a new tool to dissociate secretion of these incretin hormones and lower GIP but not GLP-1 levels in vivo.

Oxidative phosphorylation gene transcription in whitefish species pairs reveals patterns of parallel and nonparallel physiological divergence.

Across multiple lakes in North America, lake whitefish (Coregonus clupeaformis) have independently evolved 'dwarf' and 'normal' sympatric species pairs that exhibit pronounced phenotypic and genetic divergence. In particular, traits associated with metabolism have been shown to be highly differentiated between whitefish species. Here, we examine the transcription of genes associated with the five mitochondrial and nuclear genome-encoded oxidative phosphorylation (OXPHOS) complexes, the primary physiological mechanism responsible for the production of ATP, in whitefish species pairs from Cliff Lake and Webster Lake in Maine, USA. We observed OXPHOS gene transcription divergence between dwarf and normal whitefish in each of the two lakes, with the former exhibiting transcription upregulation for genes associated with each of the OXPHOS complexes. We also observed a significant influence of lake on transcription levels for some of the genes, indicating that inter-lake ecological or genetic differences are contributing to variation in OXPHOS gene transcription levels. Together, our results support the hypothesis that metabolic divergence is a critical adaptation involved in whitefish speciation and implicate OXPHOS gene upregulation as a factor involved in meeting the enhanced energetic demands of dwarf whitefish. Further studies are now needed to evaluate the contribution of genetically vs. plasticity driven variation in transcription associated with this critical physiological pathway.

Validity of triple- and dual-tracer techniques to estimate glucose appearance.

The triple-tracer (TT) dilution technique has been proposed to be the gold standard method to measure postprandial glucose appearance. However, validation against an independent standard has been missing. We addressed this issue and also validated the simpler dual-tracer (DT) technique. Sixteen young subjects with type 1 diabetes (age 19.5 ± 3.8 yr, BMI 23.4 ± 1.5 kg/m(2), HbA(1c) 8.7 ± 1.7%, diabetes duration 9.0 ± 6.9 yr, total daily insulin 0.9 ± 0.2 U·kg(-1)·day(-1), mean ± SD) received a variable intravenous 20% dextrose infusion enriched with [U-(13)C]glucose over 8 h to achieve postprandial-resembling glucose excursions while intravenous insulin was administered to achieve postprandial-resembling levels of plasma insulin. Primed [6,6-(2)H(2)]glucose was infused in a manner that mimicked the expected endogenous glucose production and [U-(13)C; 1,2,3,4,5,6,6-(2)H(7)]glucose was infused in a manner that mimicked the expected glucose appearance from a standard meal. Plasma glucose enrichment was measured by gas chromatography-mass spectrometry. The intravenous dextrose infusion served as an independent standard and was reconstructed using the TT and DT techniques with the two-compartment Radziuk/Mari model and an advanced stochastic computational method. The difference between the infused and reconstructed dextrose profile was similar for the two methods (root mean square error 6.6 ± 1.9 vs. 8.0 ± 3.5 µmol·kg(-1)·min(-1), TT vs. DT, P = NS, paired t-test). The TT technique was more accurate in recovering the overall dextrose infusion (100 ± 9 and 92 ± 12%; P = 0.02). The root mean square error associated with the mean dextrose infusion profile was 2.5 and 3.3 µmol·kg(-1)·min(-1) for the TT and DT techniques, respectively. We conclude that the TT and DT techniques combined with the advanced computational method can measure accurately exogenous glucose appearance. The TT technique tends to outperform slightly the DT technique, but the latter benefits from reduced experimental and computational complexity.

Quantitative genetic and translocation experiments reveal genotype-by-environment effects on juvenile life-history traits in two populations of Chinook salmon (Oncorhynchus tshawytscha).

Understanding the genetic architecture of phenotypic plasticity is required to assess how populations might respond to heterogeneous or changing environments. Although several studies have examined population-level patterns in environmental heterogeneity and plasticity, few studies have examined individual-level variation in plasticity. Here, we use the North Carolina II breeding design and translocation experiments between two populations of Chinook salmon to detail the genetic architecture and plasticity of offspring survival and growth. We followed the survival of 50,800 offspring through the larval stage and used parentage analysis to examine survival and growth through freshwater rearing. In one population, we found that additive genetic, nonadditive genetic and maternal effects explained 25%, 34% and 55% of the variance in larvae survival, respectively. In the second population, these effects explained 0%, 24% and 61% of the variance in larvae survival. In contrast, fry survival was regulated primarily by additive genetic effects, which indicates a shift from maternal to genetic effects as development proceeds. Fry growth also showed strong additive genetic effects. Translocations between populations revealed that offspring survival and growth varied between environments, the degree of which differed among families. These results indicate genetic differences among individuals in their degree of plasticity and consequently their ability to respond to environmental variation.

MHC genetic structure and divergence across populations of Chinook salmon (Oncorhynchus tshawytscha).

The major histocompatibility complex (MHC) is thought to be under strong selection pressure because of its integral role in pathogen recognition. Consequently, patterns of MHC genetic variation should reflect selection pressures across the landscape. We examined genetic variation and population genetic structure at the MHC class I-A1 and class II-B1 exons in five Chinook salmon (Oncorhynchus tshawytscha) populations from two geographic regions in British Columbia, Canada. We then compared estimates of population structure at the MHC genes with neutral estimates based on microsatellites to examine the potential for local adaptation at the MHC. Chinook salmon are in decline throughout much of their native range and understanding the degree of local adaptation exhibited by the MHC may be important in conservation planning. Comparisons among populations yielded higher G'(ST) estimates for the MHC class I than expected under neutrality based on the microsatellites. In contrast, the MHC class II tended to exhibit lower G'(ST) values than did the microsatellites. These results suggest that across populations unique selection pressures are driving allele frequency differences at the MHC class I but that the MHC class II may be the subject of homogenizing selection. Rates of nonsynonymous versus synonymous substitutions found in codons associated within the MHC class I and II peptide-binding regions provided strong evidence of positive selection. Together, these results support the hypothesis that selection is influencing genetic variation at the MHC, but suggest that selection pressures may vary at the two classes of loci both at the sequence and population levels.

Alanine infusion during hypoglycaemia partly supports cognitive performance in healthy human subjects.

AIM: To investigate the potential for the non-glucose metabolic substrate alanine to support brain function during glucose deprivation in man. METHODS: Seven healthy men were studied on two occasions using a hyperinsulinaemic glucose clamp to lower arterialized plasma glucose to 2.5 mmol/l, in the presence of either 2 mmol/kg/h alanine infusion or saline, measuring counter-regulatory hormonal responses, symptoms generated and cognitive function with a mini-battery of tests sensitive to hypoglycaemia. RESULTS: Alanine infusion elevated plasma alanine (peak value 1481 +/- 1260 vs. 138 +/- 32 micro mol/l, P = 0.02 alanine vs. saline) and lactate (peak value 3.09 +/- 0.14 vs. 2.05 +/- 0.12 mmol/l, P = 0.02). Cognitive function assessed by the Stroop word and colour subtests deteriorated less with alanine than saline (P < 0.01 for both). Other cognitive function tests deteriorated equally and counter-regulatory hormones rose equally during hypoglycaemia in both studies (P > 0.34) except for increased glucagon with alanine (peak 260 +/- 53 vs. 91 + 8 ng/l, P = 0.03). There was no significant effect of alanine on either autonomic or neuroglycopenic symptom scores. CONCLUSIONS: Some, but not all, aspects of cognitive performance may be supported by an alanine infusion during hypoglycaemia. It is not clear whether alanine supports brain function directly or via increased availability of lactate. These data contribute to the growing evidence that regional metabolic differences exist in the brain's ability to use non-glucose fuels during hypoglycaemia.

Characterization of the primary spinal afferent innervation of the mouse colon using retrograde labelling.

Visceral pain is the most common form of pain produced by disease and is thus of interest in the study of gastrointestinal (GI) complaints such as irritable bowel syndrome, in which sensory signals perceived as GI pain travel in extrinsic afferent neurones with cell bodies in the dorsal root ganglia (DRG). The DRG from which the primary spinal afferent innervation of the mouse descending colon arises are not well defined. This study has combined retrograde labelling and immunohistochemistry to identify and characterize these neurones. Small to medium-sized retrogradely labelled cell bodies were found in the DRG at levels T8-L1 and L6-S1. Calcitonin gene-related peptide (CGRP)- and P2X3-like immunoreactivity (LI) was seen in 81 and 32%, respectively, of retrogradely labelled cells, and 20% bound the Griffonia simplicifolia-derived isolectin IB4. CGRP-LI and IB4 were co-localized in 22% of retrogradely labelled cells, whilst P2X3-LI and IB4 were co-localized in 7% (vs 34% seen in the whole DRG population). Eighty-two per cent of retrogradely labelled cells exhibited vanilloid receptor 1-like immunoreactivity (VR1-LI). These data suggest that mouse colonic spinal primary afferent neurones are mostly peptidergic CGRP-containing, VR1-LI, C fibre afferents. In contrast to the general DRG population, a subset of neurones exist that are P2X3 receptor-LI but do not bind IB4.

Brain glucose levels are elevated in chronically hyperglycemic diabetic rats: no evidence for protective adaptation by the blood brain barrier.

Recent evidence suggests that brain function may be impaired by prolonged elevations of blood glucose, such as those that occur in poorly controlled diabetes. However, little is known about the effects of such hyperglycemia on brain metabolic substrate levels. Using microdialysis in awake, freely moving rats, we directly measured brain extracellular fluid (ECF) glucose, lactate, and beta-hydroxybutyrate (betaOHB) levels in the inferior colliculus in chronically hyperglycemic BB/wor diabetic rats and in control (Sprague-Dawley) rats during euglycemia and acute hyperglycemia. The ECF:plasma glucose ratio (0.27 to 0.34) was remarkably similar in animals from all 3 groups, resulting in proportional elevations of brain ECF glucose in the hyperglycemic groups. Moreover, brain ECF levels of lactate and beta-OHB were increased in diabetic (DM) rats as compared with controls. Our results suggest that no significant protective adaptation of the blood brain barrier (BBB) transfer of glucose occurs in chronic hyperglycemia. Hence, brain tissue may be chronically exposed to markedly elevated levels of glucose and other metabolic fuels during poorly controlled diabetes, and therefore it may be subject to the same long-term adverse effects of hyperglycemia seen in peripheral tissues.

AICAR and phlorizin reverse the hypoglycemia-specific defect in glucagon secretion in the diabetic BB rat.

Individuals with type 1 diabetes demonstrate a hypoglycemia-specific defect in glucagon secretion. To determine whether intraislet hyperinsulinemia plays a role in the genesis of this defect, glucagon-secretory responses to moderate hypoglycemia induced by either insulin or a novel combination of the noninsulin glucose-lowering agents 5-aminoimidazole-4-carboxamide (AICAR) and phlorizin were compared in diabetic BB rats (an animal model of type 1 diabetes) and nondiabetic BB rats. The phlorizin-AICAR combination was able to induce moderate and equivalent hypoglycemia in both diabetic and nondiabetic BB rats in the absence of marked hyperinsulinemia. Diabetic BB rats demonstrated impaired glucagon and epinephrine responses during insulin-induced hypoglycemia compared with nondiabetic rats. In contrast, both glucagon (9- to 10-fold increase) and epinephrine (5- to 6-fold increase) responses were markedly improved during phlorizin-AICAR hypoglycemia. Combining phlorizin, AICAR, and insulin attenuated the glucagon response to hypoglycemia by 70% in the diabetic BB rat. Phlorizin plus AICAR had no effect on counterregulatory hormones under euglycemic conditions. We conclude that alpha-cell glucagon secretion in response to hypoglycemia is not defective if intraislet hyperinsulinemia is prevented. This suggests that exogenous insulin plays a pivotal role in the etiology of this defect.

Spatial separation of light perception and growth response in maize root phototropism.

Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.