Increased insulin sensitivity and basal insulin effectiveness in postprandial reactive hypoglycaemia

Migraine, Brain Glucose Metabolism and the "Neuroenergetic" Hypothesis: A Scoping Review

Increasing evidence suggests that migraine may be the result of an impaired brain glucose metabolism. Several studies have reported brain mitochondrial dysfunction, impaired brain glucose metabolism and gray matter volume reduction in specific brain areas of migraineurs. Furthermore, peripheral insulin resistance, a condition demonstrated in several studies, may extend to the brain, leading to brain insulin resistance. This condition has been proven to downregulate insulin receptors, both in astrocytes and neurons, triggering a reduction in glucose uptake and glycogen synthesis, mainly during high metabolic demand. This scoping review examines the clinical, epidemiologic and pathophysiologic data supporting the hypothesis that abnormalities in brain glucose metabolism may generate a mismatch between the brain's energy reserve and metabolic expenditure, triggering migraine attacks. Moreover, alteration in glucose homeostasis could generate a chronic brain energy deficit promoting migraine chronification. Lastly, insulin resistance may link migraine with its comorbidities, like obesity, depression, cognitive impairment and cerebrovascular diseases. PERSPECTIVE: Although additional experimental studies are needed to support this novel "neuroenergetic" hypothesis, brain insulin resistance in migraineurs may unravel the pathophysiological mechanisms of the disease, explaining the migraine chronification and connecting migraine with comorbidities. Therefore, this hypothesis could elucidate novel potential approaches for migraine treatment.

Spontaneous Hypoglycemia After Islet Autotransplantation for Chronic Pancreatitis

CONTEXT

Spontaneous hypoglycemia has been reported in patients after total pancreatectomy (TP) and islet autotransplantation (IAT) with maintained insulin independence. Details surrounding these events have not been well described.

OBJECTIVE

The objective of the study was to determine the frequency and characteristics of spontaneous hypoglycemia in patients undergoing TP-IAT and/or to ascertain predictive or protective factors of its development.

DESIGN

This was an observational cohort study in 40 patients who underwent TP-IAT from August 2008 to May 2014, with a median follow-up of 34 months.

SETTING

The study was conducted at a single institution (Cleveland Clinic).

PATIENTS

Patients included recipients of TP-IAT.

INTERVENTION

The intervention included small, frequent meals in those patients who developed spontaneous hypoglycemia.

MAIN OUTCOME MEASURES

Incidence of spontaneous hypoglycemia development, characteristics of the patients developing hypoglycemia, and their response to small, frequent meals were measured.

RESULTS

Six of 12 patients, who maintained insulin independence, developed spontaneous hypoglycemia. The episodes could be fasting, postprandial, and/or exercise associated, with the frequency ranging from two to three times daily to once every 1-2 weeks. All patients experienced at least one episode that required external assistance, glucagon administration, and/or emergent medical attention. Patients who developed hypoglycemia had a lower median age and tended to have a lower median islet equivalent/kg body weight but a higher median total islet equivalent, body mass index, and homeostatic model assessment for insulin resistance score. All patients who received small, frequent meal intervention had improvement in severity and/or frequency of the hypoglycemic episodes.

CONCLUSIONS

Spontaneous hypoglycemia is prevalent after TP-IAT. Although the underlying pathophysiology responsible for these hypoglycemia events remains to be elucidated, small, frequent meal intervention is helpful in ameliorating this condition.

Idiopathic postprandial hyperinsulinaemic hypoglycaemia

BACKGROUND

Idiopathic postprandial hyperinsulinaemic hypoglycaemia (PPHH) has rarely been reported in the paediatric age. The objective of this study was to describe the clinical characteristics, diagnosis and management in a group of children with PPHH.

METHODS

Six children (three females) with a mean follow-up of 3.5±3.0 years at a single tertiary paediatric hospital. All had 24-h blood glucose monitoring, diagnostic fast and prolonged oral glucose tolerance test (OGTT). Follow-up included: 24-h blood glucose monitoring or continuous glucose monitoring system, prolonged OGTT and/or mixed meal (MM) test.

RESULTS

Age at diagnosis ranged from 5.4 to 15.7 years and auxology parameters were within normal range in all subjects. All the children had a normal fasting tolerance for age. Prolonged OGTT demonstrated symptomatic hypoglycaemia after 120 min in all the patients with simultaneous detectable serum insulin concentration. Acarbose was tried in three patients, having a positive effect on glycaemic and symptom control, but due to side effects, only two patients continued acarbose in the long run. Diazoxide proved to be beneficial in one patient. The rest of the patients were managed with frequent feeds but despite this, prolonged OGTT/MM demonstrated on-going PPHH.

CONCLUSIONS

Prolonged OGTT is necessary to diagnose PPHH in children. Acarbose is beneficial in children with PPHH, although not well tolerated. Patients managed exclusively on frequent feeds demonstrated persistent hypoglycaemia on OGTT. The underlying cause of the PPHH in these patients remains unknown.

Insulin response to oral stimuli and glucose effectiveness increased in neuroglycopenia following gastric bypass

OBJECTIVE

Hyperinsulinemic hypoglycemia with neuroglycopenia is a rare complication following Roux-en-Y gastric bypass (RYGB) surgery for weight management. Insulin secretion and action in response to oral and intravenous stimuli in persons with and without neuroglycopenia following RYGB are evaluated in this study.

METHODS

Cross-sectional cohort studies were performed at a single academic institution to assess insulin secretion and action during oral mixed meal tolerance test and intravenous glucose tolerance test (IVGTT).

RESULTS

Insulin secretion was increased more following oral mixed meal than intravenous glucose in individuals with neuroglycopenia compared to the asymptomatic group. Reduced insulin clearance did not contribute to higher insulinemia. Glucose effectiveness at zero insulin, estimated during the IVGTT, was also higher in those with neuroglycopenia. Insulin sensitivity did not differ between groups.

CONCLUSIONS

Increased beta-cell response to oral stimuli and insulin-independent glucose disposal may both contribute to severe hypoglycemia after RYGB.

Clinical characteristics of people experiencing biochemical hypoglycaemia during an oral glucose tolerance test: cross-sectional analyses from a UK multi-ethnic population

AIMS

People who experience biochemical hypoglycaemia during an oral glucose tolerance test (OGTT) may be insulin resistant, but this has not been investigated robustly, therefore we examined this in a population-based multi-ethnic UK study.

METHODS

Cross-sectional data from 6478 diabetes-free participants (849 with fasting insulin data available) who had an OGTT in the ADDITION-Leicester screening study (2005-2009) were analysed. People with biochemical hypoglycaemia (2-h glucose <3.3mmol/l) were compared with people with normal glucose tolerance (NGT) or impaired glucose regulation (IGR) using regression methods.

RESULTS

359 participants (5.5%) had biochemical hypoglycaemia, 1079 (16.7%) IGR and 5040 (77.8%) NGT. Biochemical hypoglycaemia was associated with younger age (P<0.01), white European ethnicity (P<0.001), higher HDL cholesterol (P<0.01), higher insulin sensitivity (P<0.05), and lower body mass index (P<0.001), blood pressure (P<0.01), fasting glucose (P<0.001), HbA1C (P<0.01), and triglycerides (P<0.01) compared with NGT and IGR separately in both unadjusted and adjusted (age, sex, ethnicity, body mass index, smoking status) models.

CONCLUSIONS

Biochemical hypoglycaemia during an OGTT in the absence of diabetes or IGR was not associated with insulin resistance, but instead appeared to be associated with more favourable glycaemic risk profiles than IGR and NGT. Thus, clinicians may not need to intervene due to biochemical hypoglycaemia on a 2-h OGTT.

Post prandial plasma glucose level less than the fasting level in otherwise healthy individuals during routine screening

During routine screening, some otherwise healthy individuals who showed remarkably lower post prandial (at 2 hour) plasma glucose without any symptom were subjected to extended glucose tolerance test and a few of them to extended post meal tolerance test as well. It was observed that post prandial (at 2 hour) plasma glucose after glucose administration was significantly lower than the fasting level (p<0.05-p<0.001). However, post prandial plasma glucose at 2 hour after their usual meal exhibited a significantly higher level than the fasting and post glucose level (p<0.05-p<0.001). Glucose appears to be a stronger agent than the more natural mixed meal in these individuals in causing post prandial lowering of plasma glucose. Hence, these individuals are to be evaluated with their usual meals before considering further investigations. Like upper limit, there is the need to have a consensus lower limit of reference interval of blood glucose level.

Ambulatory blood glucose measurement, dietary composition and physical activity levels in otherwise healthy women reporting symptoms that they attribute to hypoglycaemia

Reactive hypoglycaemia (RH) is a condition that has been popularised in the media and lay literature, particularly that targeting women, over the past 30 years. The objective of the present study was to investigate whether a non-patient group reporting symptoms that they attributed to a low blood glucose level would demonstrate biochemical hypoglycaemia when symptomatic and whether their habitual diet and activity level differed from those of controls. Thirty non-obese, healthy women (aged 19–45 years) reporting symptoms more than once a week that they attributed to hypoglycaemia (RH group), and eighteen controls, measured their finger-prick blood glucose level 3h after breakfast and lunch, and recorded their diet and activity daily for 7d. The RH group also measured their blood glucose when symptoms were being experienced. Symptoms less than 4h after eating were classed as postprandial. The mean postprandial blood glucose level in the RH group when asymptomatic (4·66 (sem 0·08) mmol/l) was significantly lower than that of controls (5·05 (sem 0·11) mmol/l; P<0·01). Symptoms occurred 2·6 (sem 0·13) h after eating, at a lower blood glucose level (4·18 (sem 0·10) mmol/l; P<0·001) than when the women were asymptomatic. On symptomatic days, the RH group were more physically active than the controls (1·64 (sem 0·04) v. 1·50 (sem 0·03) multiples of resting energyexpenditure; P<0·05), with a lower energy intake (7901 (sem 311) et al.. 9332 (sem 227) kJ; P<0·001). In conclusion, subjects reporting symptoms they associated with hypoglycaemia generally did not demonstrate biochemical hypoglycaemia but did have significantly lower blood glucose levels than controls. Higher physical activity and a failure to match energy intake to estimated energy requirement may be important in the aetiology of symptoms.

Evaluation of insulin sensitivity and glucose effectiveness during a standardized breakfast test: comparison with the minimal model analysis of an intravenous glucose tolerance test

There is a need for reliable measurements of insulin sensitivity (SI) simpler than the euglycemic hyperinsulinemic clamp or the intravenous glucose tolerance test (IVGTT), which could be used when the simpler surrogates based on fasting insulin (Ib) and glucose (Gb) lose their validity. Several evaluations of SI derived from oral glucose tolerance test (OGTT) or its physiologic form, the standardized breakfast test (SBT), have been proposed. We aimed at determining which SBT-derived measurements of SI give the best prediction of the values obtained with the minimal model analysis of an IVGTT. Twenty-eight subjects (23 females and 5 males; age, 44.3+/-0.6 years) with a wide range of glucose tolerance randomly underwent a hyperglucidic SBT and an IVGTT with minimal model analysis. Correlations of 35 indices (converted if appropriated into similar units) with IVGTT-derived SI were calculated, and the accuracy of the empiric formulas obtained with the 11 best predictions were evaluated with Bland-Altman plots. Subjects covered all the spectrum of SI between 0.19 and 21.3 min-1/(microU.mL-1)x10(-4). Eight procedures yielded satisfactory predictions of minimal model SI: (1) SI (from Matsuda's composite index)=-1.24+65/(IbGbImGm)-0.5; (2) SI=1.89+2690/(IbGbImGm); (3) SI (from Bennett's index)=-2.93+5.16/(log Ibxlog Gb); (4) SI (from Sluiter's index)=0.2+2400/(IpGp); (5) SI=-8.54+38.4/(Belfiore's ISI index); (6) SI (from Cederholm's formula)=76/(Gm log Im); (7) SI=0.248+0.947/GbIm; (8) SI (from Mari's "oral glucose insulin sensitivity" index)=oral glucose insulin sensitivity/Ip; (9) Caumo's model. Glucose effectiveness Sg can also be accurately predicted by the following formula: Sg=2.921e-0.185(G60- Gb) (Ip=insulin peak; Gp=glucose peak; Ia=insulin area; Ga=glucose area; G60=glycemia at 60 minutes). The hyperglucidic SBT can provide accurate evaluations of SI and Sg, either by elaborated models or by simple empiric formulas.

Prevalence of self-reported symptoms attributed to hypoglycaemia within a general female population of the UK

OBJECTIVE

To investigate the prevalence of symptoms attributed to hypoglycaemia that are reported by a general female population of the UK.

METHOD

A health and well-being questionnaire, including questions relating to symptoms of low blood 'sugar', medical history and anthropometry, was administered by post to 2000 randomly selected women (17-50 years) in Nottinghamshire. To avoid biasing responses, participants were not made aware of the specific focus of the study.

RESULTS

One thousand one hundred and thirty-six women returned the questionnaire (56.8% response rate). After exclusions, 37.9% of respondents reported symptoms that they attributed to hypoglycaemia, with a median of four episodes reported per month. A significant variation in the reporting of symptoms was found across body mass index (BMI) categories, with the highest prevalence of symptomatic subjects being found at the lowest BMI range (P<.05).

CONCLUSION

More than a third of women in the UK report experiencing symptoms that they attribute to hypoglycaemia. Body mass index appears to be related to the experiencing of symptoms.

Limited accuracy of surrogates of insulin resistance during puberty in obese and lean children at risk for altered glucoregulation

This study evaluated the accuracy of surrogate indexes of insulin sensitivity (SI) in children. Surrogates (homeostasis model assessment index of insulin resistance, quick insulin sensitivity index, and 40/insulin ratio index) were cross-sectionally investigated in 66 obese and lean children (17 Tanner stage I, 19 Tanner stage II-III, and 30 Tanner stage IV-V) as indexes of insulin resistance in comparison with the minimal model. The pubertal decrease in SI was found with the minimal model (-47%; P = 0.01), but not with surrogates, which were not correlated to SI. Baseline insulin (Ib) did not mirror the decrease in SI, did not significantly change when plotted against pubertal stage or age, and was not correlated to SI. Ib and surrogates were positively correlated with the body mass index. The disposition index, which quantifies the feedback between SI and insulin release, was widely scattered and decreased during puberty (P = 0.05). The specificity and sensitivity of surrogates as predictors of insulin resistance were poor (e.g. 81.1% and 30.7%, respectively, for the homeostasis model assessment index of insulin resistance). Thus, during puberty, surrogates are not accurate predictors of insulin resistance. Because reference methods are rather expensive and invasive, additional studies of alternative techniques for evaluating SI are needed to allow accurate measurement of insulin resistance in children.

Complex haplotypes of IRS2 gene are associated with severe obesity and reveal heterogeneity in the effect of Gly1057Asp mutation

In order to understand the role of the insulin receptor substrate-2 (IRS2) gene (chromosome region: 13q34) in obesity, a complex disorder associated with insulin resistance and glucose intolerance, we determined single nucleotide polymorphims (SNPs) and complex haplotypes in women with morbid obesity and a body mass index (BMI) of 41+/-0.8 kg/m2 ( n=99) compared with controls having a BMI of 23.8+/-0.1 kg/m2 ( n=92). Sequencing of unphased DNA or digestion of polymerase chain reaction fragments revealed seven SNPs, including a new C/T(-769) replacement at the 5' untranslated region. Considering four or seven SNPs, we reconstructed with the PHASE program nine or 24 haplotypes, respectively, that were well correlated into the cladogram. Logistic regression analysis with nine haplotypes in the whole sample revealed that obesity was associated with haplotype H3, with P<0.025, an odds ratio (OR) of 1.9 and a 95% confidence interval (CI) of 1.1-3.4, or pairs 3/3 ( P<0.005, OR=8.7, CI=1.9-40.1) and 3/4 ( P<0.023, OR=2.5, CI=1.1-5.6), all containing the the Gly1057Asp allelic variant of IRS2, whereas controls were associated with H5 and H6 ( P<0.02, OR=0.2, CI=0.01-0.81). Although obese H5 carriers (also containing Gly1057Asp mutation) were the most insulin resistant, haplotypes of IRS2 were poorly correlated (analysis of variance) with insulin resistance. By contrast, haplotypes H3, H4 and pairs 3/3 were consistently associated with increased 2-h glucose levels during an oral glucose tolerance test in obese individuals ( P<0.0005, 0.025 and 0.027, respectively). These data indicate that IRS2 is an influential gene in severe obesity and glucose intolerance in this population, whereas gene-based haplotypes of IRS2 have revealed heterogeneity in the behaviour of the Gly1057Asp mutation in relation to insulin resistance.

The effects of intensive training on insulin-like growth factor I (IGF-I) and IGF binding proteins 1 and 3 in competitive cyclists: relationships with glucose disposal

The aim of the present study was to determine whether 4 months of intensified training would result in modified plasma insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 1 (IGFBP-1) or IGFBP-3 in eight competitive cyclists and eight sedentary individuals and to define the relationships of these factors with glucose disposal. Insulin sensitivity and glucose effectiveness--that is, the fractional disappearance of glucose independent of any change in insulinaemia--were measured with the minimal model (mathematical analysis of frequently sampled intravenous glucose tolerance test). Both glucose effectiveness and insulin sensitivity were higher in the cyclists than in the sedentary individuals, but did not increase further with training. IGF-I was higher in the cyclists than in the sedentary group only after raining (P < 0.05). Plasma IGFBP-1 and IGFBP-3 increased after training (38 and 20%, respectively; P < 0.05) in the cyclists and were higher than in the sedentary individuals (P < 0.05). IGF-I was negatively correlated with insulin sensitivity before and after training (r = -0.66 and -0.67, respectively; P < 0.05) and IGFBP-1 was negatively correlated with glucose effectiveness before andafter training (r = -0.68 and -0.77, respectively; P < 0.05). Our results show that strenuous endurance training improves the somatotrope axis (growth hormone-IGF) and that IGFBP-1 may be involved in glucose homeostasis, possibly by limiting the exercise-induced increase in glucose disposal, in competitive cyclists.

Identification of two novel insulin receptor mutations, Asp59Gly and Leu62Pro, in type A syndrome of extreme insulin resistance

To elucidate genetic determinants of insulin resistance, we investigated insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) genes, in vitro IR function and in vivo insulin sensitivity in a family with Type A syndrome. Two missense IR mutations (Asp59Gly and Leu62Pro) found in the proband, resulted in reduction by 90% of insulin binding to erythrocytes, decreased receptor autophosphorylation and a dramatic reduction of insulin sensitivity. The proband and mother were heterozygote for Gly972Arg IRS-1 variant. Asp59Gly mutation, also carried by proband's brother with no consequence on insulin sensitivity, was inherited from the mother who is diabetic and insulin resistant and Leu62Pro was from the father. We conclude that severity of insulin resistance in the proband may be explained by the genetic condition of compound heterozygote for IR mutations while severe insulin resistance in the mother raises the possibility that other genetic factors, like IRS-1 polymorphisms, may contribute to the phenotypic expression of IR mutations.