Adaptation in brain glucose uptake following recurrent hypoglycemia

Association between time in range 70-180 mg/dl in early stage and severity with in patients acute pancreatitis

BACKGROUND

It is not well understood whether glucose control in the early stage of acute pancreatitis(AP) is related to outcome. This study aimed to investigate the association between blood glucose time in range (TIR) of 70-180 mg/dL in the first 72 h(h) on admission and the progression of AP.

METHODS

Individuals admitted with AP to the Gastroenterology Department of the Affiliated Changzhou No.2 People's Hospital of Nanjing Medical University between January 2017 and December 2021 were included and retrospectively evaluated. The percentage of TIR between 70 and 180 mg/dL in the first 72 h was calculated. According to the progress of AP at discharge, patients were divided into mild pancreatitis(MAP), and moderately severe acute pancreatitis (MSAP), or severe acute pancreatitis (SAP) groups. We examined the association between TIR or TIR ≥ 70% and AP severity using logistic regression models stratified by a glycosylated hemoglobin (HbA1c) level of 6.5%. Receiver operating characteristic (ROC) curves were generated to assess the ability of the TIR to predict MSAP or SAP.

RESULTS

A total of 298 individuals were included, of whom 35 developed MSAP or SAP. Logistic regression analyses indicated that TIR was independently associated with the incidence of more serious AP (odds ratio [OR] = 0.962, 95% CI = 0.941-0.983, p = 0.001). This association remained significant in individuals with HbA1c levels ≤ 6.5% (OR = 0.928, 95% CI = 0.888-0.969, p = 0.001). A TIR ≥ 70% was independently associated with reduced severity only in people with well-antecedent controls (OR = 0.238; 95% CI = 0.071-0.802; p = 0.020). TIR was not powerful enough to predict the severity of AP in both patients with poor antecedent glucose control (AUC = 0.641) or with HbA1c < 6.5% (AUC = 0.668).

CONCLUSIONS

TIR was independently associated with severity in patients with AP, particularly those with good antecedent glucose control.

Pathophysiology and management of hypoglycemia in diabetes

In the century since the discovery of insulin, diabetes has changed from an early death sentence to a manageable chronic disease. This change in longevity and duration of diabetes coupled with significant advances in therapeutic options for patients has fundamentally changed the landscape of diabetes management, particularly in patients with type 1 diabetes mellitus. However, hypoglycemia remains a major barrier to achieving optimal glycemic control. Current understanding of the mechanisms of hypoglycemia has expanded to include not only counter-regulatory hormonal responses but also direct changes in brain glucose, fuel sensing, and utilization, as well as changes in neural networks that modulate behavior, mood, and cognition. Different strategies to prevent and treat hypoglycemia have been developed, including educational strategies, new insulin formulations, delivery devices, novel technologies, and pharmacologic targets. This review article will discuss current literature contributing to our understanding of the myriad of factors that lead to the development of clinically meaningful hypoglycemia and review established and novel therapies for the prevention and treatment of hypoglycemia.

Glycaemic thresholds for counterregulatory hormone and symptom responses to hypoglycaemia in people with and without type 1 diabetes: a systematic review

AIM/HYPOTHESIS

The physiological counterregulatory response to hypoglycaemia is reported to be organised hierarchically, with hormone responses usually preceding symptomatic awareness and autonomic responses preceding neuroglycopenic responses. To compare thresholds for activation of these responses more accurately between people with or without type 1 diabetes, we performed a systematic review on stepped hyperinsulinaemic-hypoglycaemic glucose clamps.

METHODS

A literature search in PubMed and EMBASE was conducted. We included articles published between 1980 and 2018 involving hyperinsulinaemic stepped hypoglycaemic glucose clamps among people with or without type 1 diabetes. Key exclusion criteria were as follows: data were previously published; other patient population; a clamp not the primary intervention; and an inadequate clamp description. Glycaemic thresholds for counterregulatory hormone and/or symptom responses to hypoglycaemia were estimated and compared using generalised logrank test for interval-censored data, where the intervals were either extracted directly or calculated from the data provided by the study. A glycaemic threshold was defined as the glucose level at which the response exceeded the 95% CI of the mean baseline measurement or euglycaemic control clamp. Because of the use of interval-censored data, we described thresholds using median and IQR.

RESULTS

A total of 63 articles were included, whereof 37 papers included participants with type 1 diabetes (n=559; 67.4% male sex, aged 32.7±10.2 years, BMI 23.8±1.4 kg/m²) and 51 papers included participants without diabetes (n=733; 72.4% male sex, aged 31.1±9.2 years, BMI 23.6±1.1 kg/m²). Compared with non-diabetic control individuals, in people with type 1 diabetes, the median (IQR) glycaemic thresholds for adrenaline (3.8 [3.2-4.2] vs 3.4 [2.8-3.9 mmol/l]), noradrenaline (3.2 [3.2-3.7] vs 3.0 [2.8-3.1] mmol/l), cortisol (3.5 [3.2-4.2]) vs 2.8 [2.8-3.4] mmol/l) and growth hormone (3.8 [3.3-3.8] vs. 3.2 [3.0-3.3] mmol/l) all occurred at lower glucose levels in people with diabetes than in those without diabetes (all p≤0.01). Similarly, although both autonomic (median [IQR] 3.4 [3.4-3.4] vs 3.0 [2.8-3.4] mmol/l) and neuroglycopenic (median [IQR] 3.4 [2.8-N/A] vs 3.0 [3.0-3.1] mmol/l) symptom responses were elicited at lower glucose levels in people with type 1 diabetes, the thresholds for autonomic and neuroglycopenic symptoms did not differ for each individual subgroup.

CONCLUSIONS/INTERPRETATION

People with type 1 diabetes have glycaemic thresholds for counterregulatory hormone and symptom responses at lower glucose levels than people without diabetes. Autonomic and neuroglycopenic symptoms responses are generated at about similar levels of hypoglycaemia. There was a considerable variation in the methodology of the articles and the high insulin doses in most of the clamps may affect the counterregulatory responses.

FUNDING

This article has received funding from the Innovative Medicines Initiative 2 Joint Undertaking (JU) under grant agreement no. 777460.

REGISTRATION

This systematic review is registered in PROSPERO (CRD42019120083).

Review: experimentally induced hypoglycemia-associated autonomic failure in humans: determinants, designs and drawbacks

Context

Iatrogenic hypoglycemia remains one of the leading hindrances of optimal glycemic management in insulin-treated diabetes. Recurring hypoglycemia leads to a condition of hypoglycemia-associated autonomic failure (HAAF). HAAF refers to a combination of (i) impaired hormonal counterregulatory responses and (ii) hypoglycemia unawareness to subsequent hypoglycemia, substantially increasing the risk of severe hypoglycemia. Several studies since the 1990s have experimentally induced HAAF, yielding variable results.

Objective

The aim of this review was to assess the varying designs, clinical outcomes, potential assets, and drawbacks related to these studies.

Method

A systemic literature search was conducted on PubMed and Embase in winter 2021 to include all human studies attempting to experimentally induce HAAF. In different combinations, the search terms used were “hypoglycemia-associated autonomic failure,” “HAAF,” “hypoglycemia,” “recurring,” “recurrent,” “repeated,” “consecutive,” and “unawareness,” yielding 1565 publications. Inclusion criteria were studies that had aimed at experimentally inducing HAAF and measuring outcomes of hormonal counterregulation and awareness of hypoglycemia.

Results

The literature search yielded 27 eligible publications, of which 20 were successful in inducing HAAF while statistical significantly impairing both hormonal counterregulation and impairing awareness of hypoglycemia to subsequent hypoglycemia. Several factors were of significance as regards inducing HAAF: Foremost, the duration of antecedent hypoglycemia should be at least 90 minutes and blood glucose should be maintained below 3.4 mmol/L. Other important factors to consider are the type of participants, insulin dosage, and the risk of unintended hypoglycemia prior to the study.

Conclusion

Here we have outlined the most important factors to take into consideration when designing a study aimed at inducing HAAF, including to take into consideration other disease states susceptible to hypoglycemia, thus hopefully clarifying the field and allowing qualified studies in the future.

Rate of post-bariatric hypoglycemia using continuous glucose monitoring: A meta-analysis of literature studies

AIMS

Hypoglycemia is a serious complication of bariatric surgery. The aim of the present meta-analysis was to evaluate the rate and the timing of post-bariatric hypoglycemia (PBH) with different bariatric procedures using reliable data from continuous glucose monitoring (CGM).

DATA SYNTHESIS

Studies were systematically searched in the Web of Science, Scopus and PubMed databases according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. The prevalence of PBH was expressed as weighted mean prevalence (WMP) with pertinent 95% confidence intervals (95%CI). A total of 8 studies (16 datasets) enrolling 280 bariatric subjects were identified. The total WMP of PBH was 54.3% (95%CI: 44.5%-63.8%) while the WMP of nocturnal PBH was 16.4% (95%CI: 7.0%-34%). We found a comparable rate of PBH after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) (OR 1.62, 95%CI: 0.71-3.7; P = 0.248); likewise, the percent time spent in hypoglycemia was similar with the two procedures (mean difference 5.3%, 95%CI: -1.4%-12.0%; P = 0.122); however, RYGB was characterized by a higher glycemic variability than SG. Regression models showed that the time elapsed from surgical intervention was positively associated with a higher rate of both total PBH (Z-value: 3.32, P < 0.001) and nocturnal PBH (Z-value: 2.15, P = 0.013).

CONCLUSIONS

PBH, both post-prandial and nocturnal, is more prevalent than currently believed. The rate of PBH increases at increasing time from surgery and is comparable after RYGB and SG with a higher glucose variability after RYGB.

Insulin-Induced Recurrent Hypoglycemia Up-Regulates Glucose Metabolism in the Brain Cortex of Chemically Induced Diabetic Rats

Diabetes is a chronic metabolic disease that seriously compromises human well-being. Various studies highlight the importance of maintaining a sufficient glucose supply to the brain and subsequently safeguarding cerebral glucose metabolism. The goal of the present work is to clarify and disclose the metabolic alterations induced by recurrent hypoglycemia in the context of long-term hyperglycemia to further comprehend the effects beyond brain harm. To this end, chemically induced diabetic rats underwent a protocol of repeatedly insulin-induced hypoglycemic episodes. The activity of key enzymes of glycolysis, the pentose phosphate pathway and the Krebs cycle was measured by spectrophotometry in extracts or isolated mitochondria from brain cortical tissue. Western blot analysis was used to determine the protein content of glucose and monocarboxylate transporters, players in the insulin signaling pathway and mitochondrial biogenesis and dynamics. We observed that recurrent hypoglycemia up-regulates the activity of mitochondrial hexokinase and Krebs cycle enzymes (namely, pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and succinate dehydrogenase) and the protein levels of mitochondrial transcription factor A (TFAM). Both insults increased the nuclear factor erythroid 2–related factor 2 (NRF2) protein content and induced divergent effects in mitochondrial dynamics. Insulin-signaling downstream pathways were found to be down-regulated, and glycogen synthase kinase 3 beta (GSK3β) was found to be activated through both decreased phosphorylation at Ser9 and increased phosphorylation at Y216. Interestingly, no changes in the levels of cAMP response element-binding protein (CREB), which plays a key role in neuronal plasticity and memory, were caused by hypoglycemia and/or hyperglycemia. These findings provide experimental evidence that recurrent hypoglycemia, in the context of chronic hyperglycemia, has the capacity to evoke coordinated adaptive responses in the brain cortex that will ultimately contribute to sustaining brain cell health.

Exposure to recurrent hypoglycemia alters hippocampal metabolism in treated streptozotocin-induced diabetic rats

AIMS

Exposure to recurrent hypoglycemia (RH) is common in diabetic patients receiving glucose-lowering therapies and is implicated in causing cognitive impairments. Despite the significant effect of RH on hippocampal function, the underlying mechanisms are currently unknown. Our goal was to determine the effect of RH exposure on hippocampal metabolism in treated streptozotocin-diabetic rats.

METHODS

Hyperglycemia was corrected by insulin pellet implantation. Insulin-treated diabetic (ITD) rats were exposed to mild/moderate RH once a day for 5 consecutive days.

RESULTS

The effect of RH on hippocampal metabolism revealed 65 significantly altered metabolites in the RH group compared with controls. Several significant differences in metabolite levels belonging to major pathways (eg, Krebs cycle, gluconeogenesis, and amino acid metabolism) were discovered in RH-exposed ITD rats when compared to a control group. Key glycolytic enzymes including hexokinase, phosphofructokinase, and pyruvate kinase were affected by RH exposure.

CONCLUSION

Our results demonstrate that the exposure to RH leads to metabolomics alterations in the hippocampus of insulin-treated streptozotocin-diabetic rats. Understanding how RH affects hippocampal metabolism may help attenuate the adverse effects of RH on hippocampal functions.

Differential Resting State Connectivity Responses to Glycemic State in Type 1 Diabetes

CONTEXT

Individuals with type 1 diabetes mellitus (T1DM) have alterations in brain activity that have been postulated to contribute to the adverse neurocognitive consequences of T1DM; however, the impact of T1DM and hypoglycemic unawareness on the brain's resting state activity remains unclear.

OBJECTIVE

To determine whether individuals with T1DM and hypoglycemia unawareness (T1DM-Unaware) had changes in the brain resting state functional connectivity compared to healthy controls (HC) and those with T1DM and hypoglycemia awareness (T1DM-Aware).

DESIGN

Observational study.

SETTING

Academic medical center.

PARTICIPANTS

27 individuals with T1DM and 12 HC volunteers participated in the study.

INTERVENTION

All participants underwent blood oxygenation level dependent (BOLD) resting state functional magnetic brain imaging during a 2-step hyperinsulinemic euglycemic (90 mg/dL)-hypoglycemic (60 mg/dL) clamp.

OUTCOME

Changes in resting state functional connectivity.

RESULTS

Using 2 separate methods of functional connectivity analysis, we identified distinct differences in the resting state brain responses to mild hypoglycemia between HC, T1DM-Aware, and T1DM-Unaware participants, particularly in the angular gyrus, an integral component of the default mode network (DMN). Furthermore, changes in angular gyrus connectivity also correlated with greater symptoms of hypoglycemia (r = 0.461, P = 0.003) as well as higher scores of perceived stress (r = 0.531, P = 0.016).

CONCLUSION

These findings provide evidence that individuals with T1DM have changes in the brain's resting state connectivity patterns, which may be further associated with differences in awareness to hypoglycemia. These changes in connectivity may be associated with alterations in functional outcomes among individuals with T1DM.

Honey Supplementation and Exercise: A Systematic Review

Honey is a natural substance formed primarily of carbohydrates (~80%) which also contains a number of other compounds purported to confer health benefits when consumed. Due to its carbohydrate composition (low glycaemic index, mostly fructose and glucose), honey may theoretically exert positive effects when consumed before, during or after exercise. This review therefore appraised research examining the effects of honey consumption in combination with exercise in humans. Online database (PubMed, MEDLINE, SPORTDiscus) searches were performed, yielding 273 results. Following duplicate removal and application of exclusion criteria, nine articles were reviewed. Large methodological differences existed in terms of exercise stimulus, population, and the nutritional interventions examined. All nine studies reported biochemical variables, with four examining the effects of honey on exercise performance, whilst five described perceptual responses. Acute supplementation around a single exercise session appeared to elicit similar performance, perceptual, and immunological responses compared with other carbohydrate sources, although some performance benefit has been observed relative to carbohydrate-free comparators. When consumed over a number of weeks, honey may dampen immunological perturbations arising from exercise and possibly improve markers of bone formation. More well-controlled research is required to better understand the role for honey in a food-first approach to exercise nutrition.

Recurrent glucose deprivation leads to the preferential use of lactate by neurons in the ventromedial hypothalamus

Increased GABAergic output in the ventromedial hypothalamus (VMH) contributes to counterregulatory failure in recurrently hypoglycemic (RH) rats, and lactate, an alternate fuel source in the brain, contributes to this phenomenon. The current study assessed whether recurring bouts of glucose deprivation enhanced neuronal lactate uptake and, if so, whether this influenced γ-aminobutyric acid (GABA) output and the counterregulatory responses. Glucose deprivation was induced using 5-thioglucose (5TG). Control rats received an infusion of artificial extracellular fluid. These groups were compared with RH animals. Subsequently, the rats underwent a hypoglycemic clamp with microdialysis. To test whether 5TG affected neuronal lactate utilization, a subgroup of 5TG-treated rats was microinjected with a lactate transporter inhibitor [cyano-4-hydroxycinnamate (4CIN)] just before the start of the clamp. Both RH and 5TG raised VMH GABA levels, and this was associated with impaired counterregulatory responses. 4CIN reduced VMH GABA levels and restored the hormone responses in the 5TG group. We then evaluated [¹⁴C]lactate uptake in hypothalamic neuronal cultures. Recurring exposure to low glucose increased monocarboxylate transporter-2 mRNA expression and augmented lactate uptake. Taken together, our data suggest that glucose deprivation, per se, enhances lactate utilization in hypothalamic neurons, and this may contribute to suppression of the counterregulatory responses to hypoglycemia.

Glycemic Variability and Brain Glucose Levels in Type 1 Diabetes

The impact of glycemic variability on brain glucose transport kinetics among individuals with type 1 diabetes mellitus (T1DM) remains unclear. Fourteen individuals with T1DM (age 35 ± 4 years; BMI 26.0 ± 1.4 kg/m²; HbA_1c 7.6 ± 0.3) and nine healthy control participants (age 32 ± 4; BMI 23.1 ± 0.8; HbA_1c 5.0 ± 0.1) wore a continuous glucose monitor (Dexcom) to measure hypoglycemia, hyperglycemia, and glycemic variability for 5 days followed by ¹H MRS scanning in the occipital lobe to measure the change in intracerebral glucose levels during a 2-h glucose clamp (target glucose concentration 220 mg/dL). Hyperglycemic clamps were also performed in a rat model of T1DM to assess regional differences in brain glucose transport and metabolism. Despite a similar change in plasma glucose levels during the hyperglycemic clamp, individuals with T1DM had significantly smaller increments in intracerebral glucose levels (P = 0.0002). Moreover, among individuals with T1DM, the change in brain glucose correlated positively with the lability index (r = 0.67, P = 0.006). Consistent with findings in humans, streptozotocin-treated rats had lower brain glucose levels in the cortex, hippocampus, and striatum compared with control rats. These findings that glycemic variability is associated with brain glucose levels highlight the need for future studies to investigate the impact of glycemic variability on brain glucose kinetics.

Impact of Hypoglycemia on Brain Metabolism During Diabetes

Diabetes is a metabolic disease afflicting millions of people worldwide. A substantial fraction of world's total healthcare expenditure is spent on treating diabetes. Hypoglycemia is a serious consequence of anti-diabetic drug therapy, because it induces metabolic alterations in the brain. Metabolic alterations are one of the central mechanisms mediating hypoglycemia-related functional changes in the brain. Acute, chronic, and/or recurrent hypoglycemia modulate multiple metabolic pathways, and exposure to hypoglycemia increases consumption of alternate respiratory substrates such as ketone bodies, glycogen, and monocarboxylates in the brain. The aim of this review is to discuss hypoglycemia-induced metabolic alterations in the brain in glucose counterregulation, uptake, utilization and metabolism, cellular respiration, amino acid and lipid metabolism, and the significance of other sources of energy. The present review summarizes information on hypoglycemia-induced metabolic changes in the brain of diabetic and non-diabetic subjects and the manner in which they may affect brain function.

Impaired cognitive processing speed in type 1 diabetic patients who had severe/recurrent hypoglycaemia

AIMS

To detect whether adults with type 1 diabetes mellitus (T1DM) have lower cognitive performance than healthy individuals and to detect risk factors for low cognitive performance.

METHODS

Twenty-six adults with T1DM and twenty-six healthy subjects matched for age, gender and educational level were compared for cognitive performance by a chronometric computerized test measuring visuo-spatial working memory (N-Back) and by two validated neuropsychological tests (Mini Mental State Examination, Animal Naming Test). Clinical data about diabetes duration, average daily insulin dosage, glycated haemoglobin, retinopathy, urine albumin-creatinine ratio, previous hypoglycaemic coma and awareness of hypoglycaemia were obtained from medical records. Basal pre-test glycemia and blood pressure were measured for each patient.

RESULTS

No differences were found between patients (n = 26) and healthy controls (n = 26) in neuropsychological tests. Within diabetic patients, those with impaired awareness of hypoglycaemia (n = 7) or history of coma in the recent 1-3 years (n = 5) had psychomotor slowing at the N-Back test (592 ± 35 vs. 452 ± 21 ms and 619 ± 40 vs. 462 ± 19 ms, respectively; both p < 0.01). The variables related to diabetic severity did not show a relationship with reaction times of the N-Back test.

CONCLUSION

Psychomotor speed slowing is detectable in patients with T1DM who have a history of previous hypoglycaemic episodes or coma.

Incidence of Hypoglycemia After Gastric Bypass vs Sleeve Gastrectomy: A Randomized Trial

CONTEXT

We compared the incidence of hypoglycemia after Roux-en-Y gastric bypass (RYGB) vs sleeve gastrectomy (SG).

DESIGN, SETTING, AND MAIN OUTCOME MEASURES

Randomized, open-label trial conducted at the outpatient obesity clinic in a university hospital in Rome, Italy. The primary aim was the incidence of reactive hypoglycemia (<3.1 mmol/L after 75-g oral glucose load) at 1 year after surgery. Secondary aims were hypoglycemia under everyday life conditions, insulin sensitivity, insulin secretion, and lipid profile.

RESULTS

Of 175 eligible patients, 120 were randomized 1:1 to RYGB or SG; 117 (93%) completed the 12-month follow-up. Reactive hypoglycemia was detected in 14% and 29% of SG and RYGB patients (P = 0.079), respectively, with the effect of treatment in multivariate analysis significant at P = 0.018. Daily hypoglycemic episodes during continuous glucose monitoring did not differ between groups (P = 0.75). Four of 59 RYGB subjects (6.8%) had 1 to 3 hospitalizations for symptomatic hypoglycemia vs 0 in SG. The static β-cell glucose sensitivity index increased after both treatments (P < 0.001), but the dynamic β-cell glucose sensitivity index increased significantly in SG (P = 0.008) and decreased in RYGB (P = 0.004 for time × treatment interaction). Whole-body insulin sensitivity increased about 10-fold in both groups.

CONCLUSIONS

We show that reactive hypoglycemia is no less common after SG and is not a safer option than RYGB, but RYGB is associated with more severe hypoglycemic episodes. This is likely due to the lack of improvement of β-cell sensitivity to changes in circulating glucose after RYGB, which determines an inappropriately high insulin secretion.

Acidosis mediates recurrent hypoglycemia-induced increase in ischemic brain injury in treated diabetic rats

OBJECTIVES

Cerebral ischemia is a serious possible manifestation of diabetic vascular disease. Recurrent hypoglycemia (RH) enhances ischemic brain injury in insulin-treated diabetic (ITD) rats. In the present study, we determined the role of ischemic acidosis in enhanced ischemic brain damage in RH-exposed ITD rats.

METHODS

Diabetic rats were treated with insulin and mild/moderate RH was induced for 5 days. Three sets of experiments were performed. The first set evaluated the effects of RH exposure on global cerebral ischemia-induced acidosis in ITD rats. The second set evaluated the effect of an alkalizing agent (Tris-(hydroxymethyl)-aminomethane: THAM) on ischemic acidosis-induced brain injury in RH-exposed ITD rats. The third experiment evaluated the effect of the glucose transporter (GLUT) inhibitor on ischemic acidosis-induced brain injury in RH-exposed ITD rats. Hippocampal pH and lactate were measured during ischemia and early reperfusion for all three experiments. Neuronal survival in Cornu Ammonis 1 (CA1) hippocampus served as a measure of ischemic brain injury.

FINDINGS

Prior RH exposure increases lactate concentration and decreases pH during ischemia and early reperfusion when compared to controls. THAM and GLUT inhibitor treatments attenuated RH-induced increase in ischemic acidosis. GLUT inhibitor treatment reduced the RH-induced increase in lactate levels. Both THAM and GLUT inhibitor treatments significantly decreased ischemic damage in RH-exposed ITD rats.

CONCLUSIONS

Ischemia causes increased acidosis in RH-exposed ITD rats via a GLUT-sensitive mechanism. Exploring downstream pathways may help understand mechanisms by which prior exposure to RH increases cerebral ischemic damage.

Carbohydrates for Soccer: A Focus on Skilled Actions and Half-Time Practices

Carbohydrate consumption is synonymous with soccer performance due to the established effects on endogenous energy store preservation, and physical capacity maintenance. For performance-enhancement purposes, exogenous energy consumption (in the form of drinks, bars, gels and snacks) is recommended on match-day; specifically, before and during match-play. Akin to the demands of soccer, limited opportunities exist to consume carbohydrates outside of scheduled breaks in competition, such as at half-time. The link between cognitive function and blood glucose availability suggests that carbohydrates may influence decision-making and technical proficiency (e.g., soccer skills). However, relatively few reviews have focused on technical, as opposed to physical, performance while also addressing the practicalities associated with carbohydrate consumption when limited in-play feeding opportunities exist. Transient physiological responses associated with reductions in activity prevalent in scheduled intra-match breaks (e.g., half-time) likely have important consequences for practitioners aiming to optimize match-day performance. Accordingly, this review evaluated novel developments in soccer literature regarding (1) the ergogenic properties of carbohydrates for skill performance; and (2) novel considerations concerning exogenous energy provision during half-time. Recommendations are made to modify half-time practices in an aim to enhance subsequent performance. Viable future research opportunities exist regarding a deeper insight into carbohydrate provision on match-day.

Dissociation Between Hormonal Counterregulatory Responses and Cerebral Glucose Metabolism During Hypoglycemia

Hypoglycemia is the most common complication of diabetes, causing morbidity and death. Recurrent hypoglycemia alters the cascade of physiological and behavioral responses that maintain euglycemia. The extent to which these responses are normally triggered by decreased whole-brain cerebral glucose metabolism (CMR_glc) has not been resolved by previous studies. We measured plasma counterregulatory hormonal responses and whole-brain CMR_glc (along with blood-to-brain glucose transport rates and brain glucose concentrations) with 1-[¹¹C]-d-glucose positron emission tomography during hyperinsulinemic glucose clamps at nominal plasma glucose concentrations of 90, 75, 60, and 45 mg/dL (5.0, 4.2, 3.3, and 2.5 mmol/L) in 18 healthy young adults. Clear evidence of hypoglycemic physiological counterregulation was first demonstrated between 75 mg/dL (4.2 mmol/L) and 60 mg/dL (3.3 mmol/L) with increases in both plasma epinephrine (P = 0.01) and glucagon (P = 0.01). In contrast, there was no statistically significant change in CMR_glc (P = 1.0) between 75 mg/dL (4.2 mmol/L) and 60 mg/dL (3.3 mmol/L), whereas CMR_glc significantly decreased (P = 0.02) between 60 mg/dL (3.3 mmol/L) and 45 mg/dL (2.5 mmol/L). Therefore, the increased epinephrine and glucagon secretion with declining plasma glucose concentrations is not in response to a decrease in whole-brain CMR_glc.

Cognitive, neurophysiologic and metabolic sequelae of previous hypoglycemic coma revealed by hyperinsulinemic-hypoglycemic clamp in type 1 diabetic patients

To examine the relationship between electroencephalographic (EEG) activity and hypoglycemia unawareness, we investigated early parameters of vigilance and awareness of various symptom categories in response to hypoglycemia in intensively treated type 1 diabetic (T1DM) patients with different degrees of hypoglycemia unawareness. Hypoglycemia was induced with a hyperinsulinemic-hypoglycemic clamp in six T1DM patients with a history of hypoglycemia unawareness previous severe hypoglycemic coma (SH) and in six T1DM patients without (C) history of hypoglycemia unawareness previous severe hypoglycemic coma. Cognitive function tests (four choice reaction time), counterregulatory responses (adrenaline), and symptomatic responses were evaluated at euglycemia (90 mg/dl) and during step-wise plasma glucose reduction (68, 58 and 49 mg/dl). EEG activity was recorded continuously throughout the study and analyzed by spectral analysis. Cognitive function deteriorated significantly at a glucose threshold of 55 ± 1 mg/dl in both groups (p = ns) during hypoglycemia, while the glucose threshold for autonomic symptoms was significantly lower in SH patients than in C patients (49 ± 1 vs. 54 ± 1 mg/dl, p < 0.05, respectively). In SH patients, eye-closed resting EEG showed a correlation between the mean dominance frequency and plasma glucose (r = 0.62, p < 0.001). Theta relative power increased during controlled hypoglycemia compared to euglycemia (21.6 ± 6 vs. 15.5 ± 3% Hz p < 0.05) and was higher than in the C group (21.6 ± 6 vs. 13.8 ± 3%, p < 0.03). The cognitive task beta activity was lower in the SH group than in the C group (14.8 ± 3 Hz, vs. 22.6 ± 4 vs. p < 0.03). Controlled hypoglycemia elicits cognitive dysfunction in both C and SH patients; however, significant EEG alterations during hypoglycemia were detected mainly in patients with a history of hypoglycemia unawareness and previous severe hypoglycemic coma. These data suggest that prior episodes of hypoglycemic coma modulate brain electric activity.

Hypothalamic Glucose Transport in Humans During Experimentally Induced Hypoglycemia-Associated Autonomic Failure

CONTEXT

Upregulated brain glucose transport in response to recurrent hypoglycemia may contribute to the development of hypoglycemia-associated autonomic failure (HAAF) and impaired awareness of hypoglycemia. Whether recurrent hypoglycemia alters glucose transport in the hypothalamus is unknown.

OBJECTIVE

To test the hypothesis that hypothalamic glucose transport will increase in healthy volunteers preconditioned with recurrent hypoglycemia to induce HAAF.

SETTING

University medical center.

DESIGN AND PARTICIPANTS

Thirteen healthy subjects underwent paired euglycemic and hypoglycemic preconditioning studies separated by at least 1 month. Following preconditioning, hypothalamic glucose transport was measured by magnetic resonance spectroscopy (MRS) in the afternoon on day 2 of each preconditioning protocol.

OUTCOME MEASURE

The ratio of maximal transport rate to cerebral metabolic rate of glucose (Tmax/CMRglc), obtained from MRS-measured glucose in the hypothalamus as a function of plasma glucose.

RESULTS

HAAF was successfully induced based on lower epinephrine, glucagon, and cortisol during the third vs first hypoglycemic preconditioning clamp (P ≤ 0.01). Hypothalamic glucose transport was not different following recurrent euglycemia vs hypoglycemia (Tmax/CMRglc 1.62 ± 0.09 after euglycemia preconditioning and 1.75 ± 0.14 after hypoglycemia preconditioning; P was not significant). Hypothalamic glucose concentrations measured by MRS were not different following the two preconditioning protocols.

CONCLUSIONS

Glucose transport kinetics in the hypothalamus of healthy humans with experimentally induced HAAF were not different from those measured without HAAF. Future studies of patients with diabetes and impaired awareness of hypoglycemia will be necessary to determine if the existence of the diabetes state is required for this adaptation to hypoglycemia to occur.

Development of diabetes does not alter behavioral and molecular circadian rhythms in a transgenic rat model of type 2 diabetes mellitus

Metabolic state and circadian clock function exhibit a complex bidirectional relationship. Circadian disruption increases propensity for metabolic dysfunction, whereas common metabolic disorders such as obesity and type 2 diabetes (T2DM) are associated with impaired circadian rhythms. Specifically, alterations in glucose availability and glucose metabolism have been shown to modulate clock gene expression and function in vitro; however, to date, it is unknown whether development of diabetes imparts deleterious effects on the suprachiasmatic nucleus (SCN) circadian clock and SCN-driven outputs in vivo. To address this question, we undertook studies in aged diabetic rats transgenic for human islet amyloid polypeptide, an established nonobese model of T2DM (HIP rat), which develops metabolic defects closely recapitulating those present in patients with T2DM. HIP rats were also cross-bred with a clock gene reporter rat model (Per1:luciferase transgenic rat) to permit assessment of the SCN and the peripheral molecular clock function ex vivo. Utilizing these animal models, we examined effects of diabetes on 1) behavioral circadian rhythms, 2) photic entrainment of circadian activity, 3) SCN and peripheral tissue molecular clock function, and 4) melatonin secretion. We report that circadian activity, light-induced entrainment, molecular clockwork, as well as melatonin secretion are preserved in the HIP rat model of T2DM. These results suggest that despite the well-characterized ability of glucose to modulate circadian clock gene expression acutely in vitro, SCN clock function and key behavioral and physiological outputs appear to be preserved under chronic diabetic conditions characteristic of nonobese T2DM.

Acute bout of exercise induced prolonged muscle glucose transporter-4 translocation and delayed counter-regulatory hormone response in type 1 diabetes

Previous studies have demonstrated that an acute bout of aerobic exercise induces a subsequent delayed onset of hypoglycemia among patients with type 1 diabetes. However, the mechanisms of exercise-induced hypoglycemia in type 1 diabetes are still unclear. Streptozotocin (STZ) was injected to 6-week-old male Wistar rats, and three days after STZ injection, animals were randomly assigned into 2 groups: STZ with insulin only (STZ) and STZ with insulin and exercise (STZ+EX). Normal Wistar rats with exercise were used as control (CON+EX). Insulin was intraperitoneally injected (0.5 U/kg) to both STZ groups (-0.5 h), and a bout of aerobic exercise (15 m/min for 30 min) was conducted at euglycemic conditions (0 h). Blood was collected at 0, 1, 3, and 5 h after exercise from the carotid artery. While the blood glucose level was stable during the post-exercise period (0-5 h) in the STZ and CON+EX groups, it decreased significantly only in the STZ+EX group at 3 h. Plasma glucagon, adrenalin, and noradrenalin levels significantly increased at 1 h in the STZ group, whereas significant hormonal responses were observed at 5 h in the STZ+EX group. In skeletal muscle glucose metabolism-related pathway, the level of glucose transporter-4 (GLUT-4) translocation was significantly higher at 1 h in the CON and STZ groups. However, in the STZ+EX group, these activations were maintained by 5 h, indicating a sustained glucose metabolism in the STZ+EX group. A single bout of aerobic exercise induced a delayed onset of hypoglycemia in STZ-treated rats. A prolonged enhancement of GLUT-4 translocation and delayed counter-regulatory hormone responses may have contributed to the induction of hypoglycemia.

Cerebral blood flow response to hypoglycemia is altered in patients with type 1 diabetes and impaired awareness of hypoglycemia

It is unclear whether cerebral blood flow responses to hypoglycemia are altered in people with type 1 diabetes and impaired awareness of hypoglycemia. The aim of this study was to investigate the effect of hypoglycemia on both global and regional cerebral blood flow in type 1 diabetes patients with impaired awareness of hypoglycemia, type 1 diabetes patients with normal awareness of hypoglycemia and healthy controls ( n = 7 per group). The subjects underwent a hyperinsulinemic euglycemic-hypoglycemic glucose clamp in a 3 T MR system. Global and regional changes in cerebral blood flow were determined by arterial spin labeling magnetic resonance imaging, at the end of both glycemic phases. Hypoglycemia generated typical symptoms in patients with type 1 diabetes and normal awareness of hypoglycemia and healthy controls, but not in patients with impaired awareness of hypoglycemia. Conversely, hypoglycemia increased global cerebral blood flow in patients with impaired awareness of hypoglycemia, which was not observed in the other two groups. Regionally, hypoglycemia caused a redistribution of cerebral blood flow towards the thalamus of both patients with normal awareness of hypoglycemia and healthy controls, consistent with activation of brain regions associated with the autonomic response to hypoglycemia. No such redistribution was found in the patients with impaired awareness of hypoglycemia. An increase in global cerebral blood flow may enhance nutrient supply to the brain, hence suppressing symptomatic awareness of hypoglycemia. Altogether these results suggest that changes in cerebral blood flow during hypoglycemia contribute to impaired awareness of hypoglycemia.

Incidence and Predictive Factors of Postprandial Hyperinsulinemic Hypoglycemia After Roux-en-Y Gastric Bypass: A Five year Longitudinal Study

BACKGROUND

Postprandial hyperinsulinemic hypoglycemia (PHH) is often reported after Roux-en-Y gastric bypass (RYGB). In the absence of a prospective study, the clinical and biological determinants of PHH remain unclear.

OBJECTIVE

To determine the incidence and predictive factors of PHH after RYGB.

METHODS

Participants were 957 RYGB patients enrolled in an ongoing longitudinal cohort study. We analyzed the results of an oral glucose tolerance test (OGTT) routinely performed before surgery and 1 and/or 5 years after. PHH was defined as blood glucose < 50 mg/dL AND plasma insulin > 3 mU/L at 120 minutes post glucose challenge. Validated indices of insulin sensitivity (Matsuda index), beta-cell function (Insulinogenic index), and beta-cell mass (fasting C-peptide: glucose ratio) were calculated, from glucose, insulin, and c-peptide values measured during OGTT.

RESULTS

OGTT results were available in all patients at baseline, in 85.6% at 12 months and 52.8% at 60 months. The incidence of PHH was 0.5% at baseline, 9.1% * and 7.9%* at 12 months and 60 months following RYGB (*: P < 0.001). In multivariate logistic regression analysis, PHH after RYGB was independently associated with lower age (P = 0.005), greater weight loss (P = 0.031), as well as higher beta-cell function (P = 0.002) and insulin sensitivity (P < 0.001), but not with beta-cell mass (P = 0.381). A preoperative elevated beta-cell function was an independent predictor of PHH after RYGB (receiver operating characteristics curve area under the curve 0.68, P = 0.04).

CONCLUSIONS:

The incidence of PHH significantly increased after RYGB but remained stable between 1 and 5 years. The estimation of beta-cell function with an OGTT before surgery can identify patients at risk for developing PHH after RYGB.

Sedentary behavior as a risk factor for cognitive decline? A focus on the influence of glycemic control in brain health

Cognitive decline leading to dementia represents a global health burden. In the absence of targeted pharmacotherapy, lifestyle approaches remain the best option for slowing the onset of dementia. However, older adults spend very little time doing moderate to vigorous exercise and spend a majority of time in sedentary behavior. Sedentary behavior has been linked to poor glycemic control and increased risk of all-cause mortality. Here, we explore a potential link between sedentary behavior and brain health. We highlight the role of glycemic control in maintaining brain function and suggest that reducing and replacing sedentary behavior with intermittent light-intensity physical activity may protect against cognitive decline by reducing glycemic variability. Given that older adults find it difficult to achieve current exercise recommendations, this may be an additional practical strategy. However, more research is needed to understand the impact of poor glycemic control on brain function and whether practical interventions aimed at reducing and replacing sedentary behavior with intermittent light intensity physical activity can help slow cognitive decline.

Glycogen Supercompensation in the Rat Brain After Acute Hypoglycemia is Independent of Glucose Levels During Recovery

Patients with diabetes display a progressive decay in the physiological counter-regulatory response to hypoglycemia, resulting in hypoglycemia unawareness. The mechanism through which the brain adapts to hypoglycemia may involve brain glycogen. We tested the hypothesis that brain glycogen supercompensation following hypoglycemia depends on blood glucose levels during recovery. Conscious rats were submitted to hypoglycemia of 2 mmol/L for 90 min and allowed to recover at different glycemia, controlled by means of i.v. glucose infusion. Brain glycogen concentration was elevated above control levels after 24 h of recovery in the cortex, hippocampus and striatum. This glycogen supercompensation was independent of blood glucose levels in the post-hypoglycemia period. In the absence of a preceding hypoglycemia insult, brain glycogen concentrations were unaltered after 24 h under hyperglycemia. In the hypothalamus, which controls peripheral glucose homeostasis, glycogen levels were unaltered. Overall, we conclude that post-hypoglycemia glycogen supercompensation occurs in several brain areas and its magnitude is independent of plasma glucose levels. By supporting brain metabolism during recurrent hypoglycemia periods, glycogen may have a role in the development of hypoglycemia unawareness.

Migraine: A disorder of metabolism?

The treatment and prevention of migraine within the last decade has become largely pharmacological. While there is little doubt that the advent of drugs (e.g. triptans) has helped many migraine sufferers to lead a normal life, there is still little knowledge with respect to the factors responsible for precipitating a migraine attack. Evidence from biochemical and behavioural studies from a number of disciplines is integrated to put forward the proposal that migraine is part of a cascade of events, which together act to protect the organism when confronted by a metabolic challenge.

Metabolic pathways in the periphery and brain: Contribution to mental disorders?

The association between mental disorders and diabetes has a long history. Recent large-scale, well-controlled epidemiological studies confirmed a link between diabetes and psychiatric illnesses. The scope of this review is to summarize our current understanding of this relationship from a molecular perspective. We first discuss the potential contribution of diabetes-associated metabolic impairments to the etiology of mental conditions. Then, we focus on possible shared molecular risk factors and mechanisms. Simple comorbidity, shared susceptibility loci, and common pathophysiological processes in diabetes and mental illnesses have changed our traditional way of thinking about mental illness. We conclude that schizophrenia and affective disorders are not limited to an imbalance in dopaminergic and serotoninergic neurotransmission in the brain. They are also systemic disorders that can be considered, to some extent, as metabolic disorders.

Gastric Bypass Reduces Symptoms and Hormonal Responses in Hypoglycemia

Gastric bypass (GBP) surgery, one of the most common bariatric procedures, induces weight loss and metabolic effects. The mechanisms are not fully understood, but reduced food intake and effects on gastrointestinal hormones are thought to contribute. We recently observed that GBP patients have lowered glucose levels and frequent asymptomatic hypoglycemic episodes. Here, we subjected patients before and after undergoing GBP surgery to hypoglycemia and examined symptoms and hormonal and autonomic nerve responses. Twelve obese patients without diabetes (8 women, mean age 43.1 years [SD 10.8] and BMI 40.6 kg/m(2) [SD 3.1]) were examined before and 23 weeks (range 19-25) after GBP surgery with hyperinsulinemic-hypoglycemic clamp (stepwise to plasma glucose 2.7 mmol/L). The mean change in Edinburgh Hypoglycemia Score during clamp was attenuated from 10.7 (6.4) before surgery to 5.2 (4.9) after surgery. There were also marked postsurgery reductions in levels of glucagon, cortisol, and catecholamine and the sympathetic nerve responses to hypoglycemia. In addition, growth hormone displayed a delayed response but to a higher peak level. Levels of glucagon-like peptide 1 and gastric inhibitory polypeptide rose during hypoglycemia but rose less postsurgery compared with presurgery. Thus, GBP surgery causes a resetting of glucose homeostasis, which reduces symptoms and neurohormonal responses to hypoglycemia. Further studies should address the underlying mechanisms as well as their impact on the overall metabolic effects of GBP surgery.

Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies

Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain's handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.

Metabolic Alterations Associated to Brain Dysfunction in Diabetes

From epidemiological studies it is known that diabetes patients display increased risk of developing dementia. Moreover, cognitive impairment and Alzheimer's disease (AD) are also accompanied by impaired glucose homeostasis and insulin signalling. Although there is plenty of evidence for a connection between insulin-resistant diabetes and AD, definitive linking mechanisms remain elusive. Cerebrovascular complications of diabetes, alterations in glucose homeostasis and insulin signalling, as well as recurrent hypoglycaemia are the factors that most likely affect brain function and structure. While difficult to study in patients, the mechanisms by which diabetes leads to brain dysfunction have been investigated in experimental models that display phenotypes of the disease. The present article reviews the impact of diabetes and AD on brain structure and function, and discusses recent findings from translational studies in animal models that link insulin resistance to metabolic alterations that underlie brain dysfunction. Such modifications of brain metabolism are likely to occur at early stages of neurodegeneration and impact regional neurochemical profiles and constitute non-invasive biomarkers detectable by magnetic resonance spectroscopy (MRS).

Half-time strategies to enhance second-half performance in team-sports players: a review and recommendations

A number of intermittent team sports require that two consecutive periods of play (lasting for ~30-45 min) are separated by a 10-20 min half-time break. The half-time practices employed by team-sports players generally include returning to the changing rooms, temporarily relaxing from the cognitive and physical demands of the first half, rehydration and re-fuelling strategies, addressing injury or equipment concerns, and receiving tactical instruction and coach feedback. However, the typically passive nature of these actions has been associated with physiological changes that impair performance during the second half. Both physical and cognitive performances have been found to decline in the initial stages of subsequent exercise that follows half-time. An increased risk of injury has also been observed during this period. Therefore, half-time provides sports scientists and strength and conditioning coaches with an opportunity to optimise second-half performance. An overview of strategies thought to benefit team-sports athletes is presented; specifically, the efficacy of heat maintenance strategies (including passive and active methods), post-activation potentiation, hormonal priming, and modified hydro-nutritional practices are discussed. A theoretical model of applying these strategies in a manner that compliments current practice is also offered.

Hypoglycemia in everyday life after gastric bypass and duodenal switch

DESIGN

Gastric bypass (GBP) and duodenal switch (DS) in morbid obesity are accompanied by marked metabolic improvements, particularly in glucose control. In recent years, episodes of severe late postprandial hypoglycemia have been increasingly described in GBP patients; data in DS patients are scarce. We recruited three groups of subjects; 15 GBP, 15 DS, and 15 non-operated overweight controls to examine to what extent hypoglycemia occurs in daily life.

METHODS

Continuous glucose monitoring (CGM) was used during 3 days of normal activity. The glycemic variability was measured by mean amplitude of glycemic excursion and continuous overall net glycemic action. Fasting blood samples were drawn, and the patients kept a food and symptom log throughout the study.

RESULTS

The GBP group displayed highly variable CGM curves, and 2.9% of their time was spent in hypoglycemia (<3.3  mmol/l, or 60  mg/dl). The DS group had twice as much time in hypoglycemia (5.9%) and displayed CGM curves with little variation as well as lower HbA1c levels (29.3 vs 35.9 mmol/mol, P<0.05). Out of a total of 72 hypoglycemic episodes registered over the 3-day period, 70 (97%) occurred in the postprandial state and only about one-fifth of the hypoglycemic episodes in the GBP and DS groups were accompanied by symptoms. No hypoglycemias were seen in controls during the 3-day period.

CONCLUSION

Both types of bariatric surgery induce marked, but different, changes in glucose balance accompanied by frequent, but mainly unnoticed, hypoglycemic episodes. The impact and mechanism of hypoglycemic unawareness after weight-reduction surgery deserves to be clarified.

Carbohydrate ingestion before and during soccer match play and blood glucose and lactate concentrations

CONTEXT

The ingestion of carbohydrate (CHO) before and during exercise and at halftime is commonly recommended to soccer players for maintaining blood glucose concentrations throughout match play. However, an exercise-induced rebound glycemic response has been observed in the early stages of the second half of simulated soccer-specific exercise when CHO-electrolyte beverages were consumed regularly. Therefore, the metabolic effects of CHO beverage consumption throughout soccer match play remain unclear.

OBJECTIVE

To investigate the blood glucose and blood lactate responses to CHOs ingested before and during soccer match play.

DESIGN

Crossover study.

SETTING

Applied research study.

PATIENTS OR OTHER PARTICIPANTS

Ten male outfield academy soccer players (age = 15.6 ± 0.2 years, height = 1.74 ± 0.02 m, mass = 65.3 ± 1.9 kg, estimated maximal oxygen consumption = 58.4 ± 0.8 mL·kg(-1)·min(-1)).

INTERVENTION(S)

Players received a 6% CHO-electrolyte solution or an electrolyte (placebo) solution 2 hours before kickoff, before each half (within 10 minutes), and every 15 minutes throughout exercise. Blood samples were obtained at rest, every 15 minutes during the match (first half: 0-15, 15-30, and 30-45 minutes; second half: 45-60, 60-75, and 75-90 minutes) and 10 minutes into the halftime break.

MAIN OUTCOME MEASURE(S)

Metabolic responses (blood glucose and blood lactate concentrations) and markers of exercise intensity (heart rate) were recorded.

RESULTS

Supplementation influenced the blood glucose response to exercise (time × treatment interaction effect: P ≤ .05), such that glucose concentrations were higher at 30 to 45 minutes in the CHO than in the placebo condition. However, in the second half, blood glucose concentrations were similar between conditions because of transient reductions from peak values occurring in both trials at halftime. Blood lactate concentrations were elevated above those at rest in the first 15 minutes of exercise (time-of-sample effect: P < .001) and remained elevated throughout exercise. Supplementation did not influence the pattern of response (time × treatment interaction effect: P = .49).

CONCLUSIONS

Ingestion of a 6% CHO-electrolyte beverage before and during soccer match play did not benefit blood glucose concentrations throughout the second half of exercise.

Banting memorial lecture 2013. A life in balance: wandering the pathways of control

‘To keep in equilibrium’, one of the Oxford English Dictionary’s many definitions of balance, is a desirable target for anylife, but has special meaning for the life of a person with diabetes. Achieving balance—between hypo- and hyperglycaemia; between energy intake and energy consumption; between insulin action and insulin secretion; between attention to diabetes and attention to everything else—remains challenging, but progress has been made over the last three decades, both in our understanding of how nature achieves balance and in the tools we have to try to reproduce the actions of nature in disease states. In particular, the role of the brain in controlling diabetes, from glucose sensing to decision making, has been investigated. Physiological and neuro-imaging studies are finally being translated into patient benefit, with the aim of improving, as Dr Banting put it, the provision of ‘energy for the economic burdens of life’.

The effects of endurance training and thiamine supplementation on anti-fatigue during exercise

The purpose of this study was to find the effect of endurance training and thiamine supplementation on anti-fatigue during the exercise. Each nine students from K Women's University went through three cross-over treatments: placebo treatment, training treatment and thiamine treatment. Training treatment was performed with bicycle ergometer exercise for four weeks (five days per week). Each exercise was performed for an hour with intensity set at 70% (50rpm) of maximal oxygen uptake. Thiamine treatment group was given 10mg of thiamine tetrahydrofurfuryl disulfide per one kilogram for four weeks. The bicycle ergometer exercise was performed at 70% of maximal oxygen uptake in exercise intensity which 60 minutes of exercise was performed at 50rpm . Lactate concentration was significantly decreased during 15 to 30 minutes of exercise for those with training treatment and 15 to 60 minutes of exercise for those with thiamine treatment compared to placebo treatment group. Ammonia concentration was significantly decreased during 15 to 60 minutes of exercise and 15 to 30 minutes of recovery for those with training and thiamine treatment compared to placebo treatment. Resting blood thiamine concentrations of placebo treatment were significantly lower than training treatment. 60 minutes after the exercise, plasma thiamine concentration was significantly increased in all treatment group. To sum up the previous, thiamine intake during exercise positively benefits carbohydrate metabolism in a way that will decrease lactate concentration, ammonia concentration, and anti- fatigue by reducing the RPE. Therefore, we can consider thiamine intake to be utilized as similar benefits as endurance training.

Hypoglycemia in patients with type 1 diabetes: epidemiology, pathogenesis, and prevention

Hypoglycemia is uncommon in the general, nondiabetic population but occurs frequently in persons with diabetes treated with insulin or insulin secretagogues. Thus, iatrogenic hypoglycemia explains the majority of cases among persons with type 1 diabetes (T1DM). Since T1DM is characterized by absolute insulin dependence, the current imperfections in insulin replacement therapies often lead to a mismatch between caloric supply and circulating insulin levels, thus increasing the risk for glycemic fluctuations. Hypoglycemia is the limiting factor to excellent glycemic control in insulin-treated subjects. Intensification of glycemic control was associated with a 300 % increase in the rate of hypoglycemia in the Diabetes Control and Complications Trial. Recent measurements using continuous glucose monitoring reveal an alarming rate of daytime and nocturnal episodes of hypoglycemia in patients with T1DM. Etiological factors underlying hypoglycemia in T1DM include predictable triggers (skipped meals, exercise, insulin over dosage) as well as defective counterregulation, a component of hypoglycemia-associated autonomic failure.

Glucagon-like peptide-1 (GLP-1) raises blood-brain glucose transfer capacity and hexokinase activity in human brain

In hyperglycemia, glucagon-like peptide-1 (GLP-1) lowers brain glucose concentration together with increased net blood-brain clearance and brain metabolism, but it is not known whether this effect depends on the prevailing plasma glucose (PG) concentration. In hypoglycemia, glucose depletion potentially impairs brain function. Here, we test the hypothesis that GLP-1 exacerbates the effect of hypoglycemia. To test the hypothesis, we determined glucose transport and consumption rates in seven healthy men in a randomized, double-blinded placebo-controlled cross-over experimental design. The acute effect of GLP-1 on glucose transfer in the brain was measured by positron emission tomography (PET) during a hypoglycemic clamp (3 mM plasma glucose) with (18)F-fluoro-2-deoxy-glucose (FDG) as tracer of glucose. In addition, we jointly analyzed cerebrometabolic effects of GLP-1 from the present hypoglycemia study and our previous hyperglycemia study to estimate the Michaelis-Menten constants of glucose transport and metabolism. The GLP-1 treatment lowered the vascular volume of brain tissue. Loading data from hypo- to hyperglycemia into the Michaelis-Menten equation, we found increased maximum phosphorylation velocity (V max) in the gray matter regions of cerebral cortex, thalamus, and cerebellum, as well as increased blood-brain glucose transport capacity (T max) in gray matter, white matter, cortex, thalamus, and cerebellum. In hypoglycemia, GLP-1 had no effects on net glucose metabolism, brain glucose concentration, or blood-brain glucose transport. Neither hexokinase nor transporter affinities varied significantly with treatment in any region. We conclude that GLP-1 changes blood-brain glucose transfer and brain glucose metabolic rates in a PG concentration-dependent manner. One consequence is that hypoglycemia eliminates these effects of GLP-1 on brain glucose homeostasis.

The effect of diabetes mellitus on the association between measures of glycaemic control and ICU mortality: a retrospective cohort study

INTRODUCTION

In critical illness, four measures of glycaemic control are associated with ICU mortality: mean glucose concentration, glucose variability, the incidence of hypoglycaemia (≤2.2 mmol/l) or low glucose (2.3 to 4.7 mmol/l). Underlying diabetes mellitus (DM) might affect these associations. Our objective was to study whether the association between these measures of glycaemic control and ICU mortality differs between patients without and with DM and to explore the cutoff value for detrimental low glucose in both cohorts.

METHODS

This retrospective database cohort study included patients admitted between January 2004 and June 2011 to a 24-bed medical/surgical ICU in a teaching hospital. We analysed glucose and outcome data from 10,320 patients: 8,682 without DM and 1,638 with DM. The cohorts were subdivided into quintiles of mean glucose and quartiles of glucose variability. Multivariable regression models were used to examine the independent association between the four measures of glycaemic control and ICU mortality, and for defining the cutoff value for detrimental low glucose.

RESULTS

Regarding mean glucose, a U-shaped relation was observed in the non-DM cohort with an increased ICU mortality in the lowest and highest glucose quintiles (odds ratio=1.4 and 1.8, P<0.001). No clear pattern was found in the DM cohort. Glucose variability was related to ICU mortality only in the non-DM cohort, with highest ICU mortality in the upper variability quartile (odds ratio=1.7, P<0.001). Hypoglycaemia was associated with ICU mortality in both cohorts (odds ratio non-DM=2.5, P<0.001; odds ratio DM=4.2, P=0.001), while low-glucose concentrations up to 4.9 mmol/l were associated with an increased risk of ICU mortality in the non-DM cohort and up to 3.5 mmol/l in the DM cohort.

CONCLUSION

Mean glucose and high glucose variability are related to ICU mortality in the non-DM cohort but not in the DM cohort. Hypoglycaemia (≤2.2 mmol/l) was associated with ICU mortality in both. The cutoff value for detrimental low glucose is higher in the non-DM cohort (4.9 mmol/l) than in the DM cohort (3.5 mmol/l). While hypoglycaemia (≤2.2 mmol/l) should be avoided in both groups, DM patients seem to tolerate a wider glucose range than non-DM patients.

Defective counterregulation and hypoglycemia unawareness in diabetes: mechanisms and emerging treatments

For people with diabetes, hypoglycemia remains the limiting factor in achieving glycemic control. This article reviews recent advances in how the brain senses and responds to hypoglycemia. Novel mechanisms by which individuals with insulin-treated diabetes develop hypoglycemia unawareness and impaired counterregulatory responses are outlined. Prevention strategies for reducing the incidence of hypoglycemia are discussed.

Metabolic neuroimaging of the brain in diabetes mellitus and hypoglycaemia

Functional neuroimaging techniques can be used to study changes in regional brain activation, using changes in surrogate markers such as regional cerebral perfusion and rates of glucose uptake or metabolism. These approaches are shedding new light on two major health problems: the increasing burden of type 2 diabetes mellitus (T2DM), which is driven by the rising prevalence of insulin resistance and obesity; and recurrent intractable problematic hypoglycaemia, which is driven by the cognitive impairment that can occur in association with iatrogenic hypoglycaemic episodes. Some patients with diabetes mellitus lose awareness of being hypoglycaemic, which puts them at risk of severe hypoglycaemia as they are unlikely to take action to prevent the condition worsening. Involvement of corticolimbic brain and centres serving higher executive functions as well as the hypothalamus has been demonstrated in both situations and has implications for therapy. This Review describes the relevant principles of functional neuroimaging techniques and presents data supporting the notion that the dysregulation of central pathways involved in metabolic regulation, reward and appetite could contribute to problematic hypoglycaemia during therapy for diabetes mellitus and to insulin-resistant obesity and T2DM. Understanding these dysregulations could enable the development of novel clinical interventions.

The Kety-Schmidt technique for quantitative perfusion and oxygen metabolism measurements in the MR imaging environment

SUMMARY

The Kety-Schmidt technique provides quantitative measurement of whole-brain CBF. CBF is measured as the area between the arterial and venous washout curves of a diffusible tracer. Oxygen extraction and metabolism may be calculated from arterial and venous samples. In this report, we present a method for performing these measurements in an MR imaging environment. This technique could be useful for validation of MR imaging methods of hemodynamic and metabolic measurements in humans.

Striatal dopamine receptors modulate the expression of insulin receptor, IGF-1 and GLUT-3 in diabetic rats: effect of pyridoxine treatment

The incidence of type 2 diabetes mellitus is rising at alarming proportions. Central nervous system plays an important part in orchestrating glucose metabolism, with accumulating evidence linking dysregulated central nervous system circuits to the failure of normal glucoregulatory mechanisms. Pyridoxine is a water soluble vitamin and it has important role in brain function. This study aims to evaluate the role of pyridoxine in striatal glucose regulation through dopaminergic receptor expressions in streptozotocin induced diabetic rats. Radio receptor binding assays for dopamine D(1), D(2) receptors were done using [(3)H] 7-chloro-3-methyl-1-phenyl-1,2,4,5-tetrahydro-3-benzazepin-8-ol and [(3)H] 5-chloro-2-methoxy-4-methylamino-N-[-2-methyl-1-(phenylmethyl)pyrrolidin-3-yl]benzamide. Gene expressions were done using fluorescently labeled Taqman probes of dopamine D(1), D(2) receptor, Insulin receptor, Insulin like growth factor-1(IGF-1) and Glucose transporter-3 (GLUT-3). Bmax of dopamine D(1) receptor is decreased and B(max) of dopamine D(2) was increased in diabetic rats compared to control. Gene expression of dopamine D(1) receptor was down regulated and dopamine D(2) receptor was up regulated in diabetic rats. Our results showed decreased gene expression of Insulin receptor, IGF-1 and increased gene expression of GLUT-3 in diabetic rats compared to control. Pyridoxine treatment restored diabetes induced alterations in dopamine D(1), D(2) receptors, Insulin receptor, IGF-1, GLUT-3 gene expressions in striatum compared to diabetic rats. Insulin treatment reversed dopamine D(1), D(2) receptor, GLUT-3 mRNA expression, D(2) receptor binding parameters in the striatum compared to diabetic group. Our results suggest the potential role of pyridoxine supplementation in ameliorating diabetes mediated dysfunctions in striatal dopaminergic receptor expressions and insulin signaling. Thus pyridoxine has therapeutic significance in diabetes management.

Interacting epidemics? Sleep curtailment, insulin resistance, and obesity

In the last 50 years, the average self-reported sleep duration in the United States has decreased by 1.5-2 hours in parallel with an increasing prevalence of obesity and diabetes. Epidemiological studies and meta-analyses report a strong relationship between short or disturbed sleep, obesity, and abnormalities in glucose metabolism. This relationship is likely to be bidirectional and causal in nature, but many aspects remain to be elucidated. Sleep and the internal circadian clock influence a host of endocrine parameters. Sleep curtailment in humans alters multiple metabolic pathways, leading to more insulin resistance, possibly decreased energy expenditure, increased appetite, and immunological changes. On the other hand, psychological, endocrine, and anatomical abnormalities in individuals with obesity and/or diabetes can interfere with sleep duration and quality, thus creating a vicious cycle. In this review, we address mechanisms linking sleep with metabolism, highlight the need for studies conducted in real-life settings, and explore therapeutic interventions to improve sleep, with a potential beneficial effect on obesity and its comorbidities.

[Changes in cognitive function in patients with diabetes mellitus]

Patients with diabetes are approximately 1.5 times more likely to experience cognitive decline than individuals without diabetes mellitus. Most of the data suggest that patients with diabetes have reduced performance in numerous domains of cognitive function. In patients with type 1 diabetes, specific and global deficits involving speed of psychomotor efficiency, information processing, mental flexibility, attention, and visual perception seem to be present, while in patients with type 2 diabetes an increase in memory deficits, a reduction in psychomotor speed, and reduced frontal lobe (executive) functions have been found. The complex pathophysiology of changes in the central nervous system in diabetes has not yet been fully elucidated. It is important to consider the patient's age at the onset of diabetes, the glycemic control status, and the presence of diabetic complications. Neurological consequences of diabetes appear parallel to those observed in the aging brain. Neuroimaging studies highlight several structural cerebral changes, cortical and subcortical atrophy, beside increased leukoaraiosis that occurs in association with diabetes. There is supporting evidence from many hypotheses to explain the pathophysiology of cognitive decline associated with diabetes. The main hypotheses pointing to the potential, implied mechanisms involve hyperglycemia, hypoglycemia, microvascular disease, insulin resistance, hyperinsulinism, hyperphosphorylation of tau protein, and amyloid-β deposition.

Insulin therapy and hypoglycemia

Hypoglycemia is the most important and common side effect of insulin therapy. It is also the rate limiting factor in safely achieving excellent glycemic control. A three-fold increased risk of severe hypoglycemia occurs in both type 1 and type 2 diabetes with tight glucose control. This dictates a need to individualize therapy and glycemia goals to minimize this risk. Several ways to reduce hypoglycemia risk are recognized and discussed. They include frequent monitoring of blood sugars with home blood glucose tests and sometimes continuous glucose monitoring (CGM) in order to identify hypoglycemia particularly in hypoglycemia unawareness. Considerations include prompt measured hypoglycemia treatment, attempts to reduce glycemic variability, balancing basal and meal insulin therapy, a pattern therapy approach and use of a physiological mimicry with insulin analogues in a flexible manner. Methods to achieve adequate control while focusing on minimizing the risk of hypoglycemia are delineated in this article.

Brain glycogen content and metabolism in subjects with type 1 diabetes and hypoglycemia unawareness

Supercompensated brain glycogen may contribute to the development of hypoglycemia unawareness in patients with type 1 diabetes by providing energy for the brain during periods of hypoglycemia. Our goal was to determine if brain glycogen content is elevated in patients with type 1 diabetes and hypoglycemia unawareness. We used in vivo (13)C nuclear magnetic resonance spectroscopy in conjunction with [1-(13)C]glucose administration in five patients with type 1 diabetes and hypoglycemia unawareness and five age-, gender-, and body mass index-matched healthy volunteers to measure brain glycogen content and metabolism. Glucose and insulin were administered intravenously over ∼51 hours at a rate titrated to maintain a blood glucose concentration of 7 mmol/L. (13)C-glycogen levels in the occipital lobe were measured at ∼5, 8, 13, 23, 32, 37, and 50 hours, during label wash-in and wash-out. Newly synthesized glycogen levels were higher in controls than in patients (P<0.0001) for matched average blood glucose and insulin levels, which may be due to higher brain glycogen content or faster turnover in controls. Metabolic modeling indicated lower brain glycogen content in patients than in controls (P=0.07), implying that glycogen supercompensation does not contribute to the development of hypoglycemia unawareness in humans with type 1 diabetes.

Hypoglycemia in critically ill children

BACKGROUND

The practice of glycemic control with intravenous insulin in critically ill patients has brought clinical focus on understanding the effects of hypoglycemia, especially in children. Very little is published on the impact of hypoglycemia in this population. We aimed to review the existing literature on hypoglycemia in critically ill neonates and children.

METHODS

We performed a systematic review of the literature up to August 2011 using PubMed, Ovid MEDLINE and ISI Web of Science using the search terms "hypoglycemia or hypoglyc*" and "critical care or intensive care or critical illness". Articles were limited to "all child (0-18 years old)" and "English".

RESULTS

A total of 513 articles were identified and 132 were included for review. Hypoglycemia is a significant concern among pediatric and neonatal intensivists. Its definition is complicated by the use of a biochemical measure (i.e., blood glucose) for a pathophysiologic problem (i.e., neuroglycopenia). Based on associated outcomes, we suggest defining hypoglycemia as <40-45 mg/dl in neonates and <60-65 mg/dl in children. Below the suggested threshold values, hypoglycemia is associated with worse neurological outcomes, increased intensive care unit stay, and increased mortality. Disruptions in carbohydrate metabolism increase the risk of hypoglycemia incritically ill children. Prevention of hypoglycemia, especially in the setting of intravenous insulin use, will be best accomplished by the combination of accurate measuring techniques, frequent or continuous glucose monitoring, and computerized insulin titration protocols.

CONCLUSION

Studies on hypoglycemia in critically ill children have focused on spontaneous hypoglycemia. With the current practice of maintaining blood glucose within a narrow range with intravenous insulin, the risk factors and outcomes associated with insulin-induced hypoglycemia should be rigorously studied to prevent hypoglycemia and potentially improve outcomes of critically ill children.