Thirty years of research on the dawn phenomenon: lessons to optimize blood glucose control in diabetes

Akkermansia muciniphila supplementation improves glucose tolerance in intestinal Ffar4 knockout mice during the daily light to dark transition

IMPORTANCE

Alterations in the intestinal environment are associated with various diseases, and FFAR4 is abundantly enriched in the intestine, where it has been shown to have the ability to regulate intestinal hormone secretion and intestinal microbiota; here, we confirmed previous reports. Meanwhile, we found that intestinal FFAR4 regulates glucagon-like peptide 1 secretion by decreasing Akkermansia muciniphila abundance and show that such change is associated with the level of glucose utilization at ZT12 in mice. Intestinal FFAR4 deficiency leads to severely impaired glucose tolerance at the ZT12 moment in mice, and Akkermansia muciniphila supplementation ameliorates the abnormal glucose utilization at the ZT12 moment caused by FFAR4 deficiency, which is very similar to the dawn phenomenon in diabetic patients. Collectively, our data suggest that intestinal Ffar4 deteriorates glucose tolerance at the daily light to dark transition by affecting Akkermansia muciniphila.

Diurnal Cycling of Insulin Sensitivity in Type 2 Diabetes: Evidence for Deviation From Physiology at an Early Stage

The aim of this study was to establish the contribution of insulin resistance to the morning (a.m.) versus afternoon (p.m.) lower glucose tolerance of people with type 2 diabetes (T2D). Eleven subjects with T2D (mean [SD] diabetes duration 0.79 [0.23] years, BMI 28.3 [1.8] kg/m2, A1C 6.6% [0.26%] [48.9 (2.9) mmol/mol]), treatment lifestyle modification only) and 11 matched control subjects without diabetes were monitored between 5:00 and 8:00 a.m. and p.m. (in random order) on one occasion (study 1), and on a subsequent occasion, they underwent an isoglycemic clamp (a.m. and p.m., both between 5:00 and 8:00, insulin infusion rate 10 mU/m2/min) (study 2). In study 1, plasma glucose, insulin, C-peptide, and glucagon were higher and insulin clearance lower in subjects with T2D a.m. versus p.m. and versus control subjects (P < 0.05), whereas free fatty acid, glycerol, and β-hydroxybutyrate were lower a.m. versus p.m. However, in study 2 at identical hyperinsulinemia a.m. and p.m. (∼150 pmol/L), glucose Ra and glycerol Ra were both less suppressed a.m. versus p.m. (P < 0.05) in subjects with T2D. In contrast, in control subjects, glucose Ra was more suppressed a.m. versus p.m. Leucine turnover was no different a.m. versus p.m. In conclusion, in subjects with T2D, insulin sensitivity for glucose (liver) and lipid metabolism has diurnal cycles (nadir a.m.) opposite that of control subjects without diabetes already at an early stage, suggesting a marker of T2D.

ARTICLE HIGHLIGHTS

In people with type 2 diabetes (T2D), fasting hyperglycemia is greater in the morning (a.m.) versus the afternoon (p.m.), and insulin sensitivity for glucose and lipid metabolism is lower a.m. versus p.m. This pattern is the reverse of the physiological diurnal cycle of people without diabetes who are more insulin sensitive a.m. versus p.m. These new findings have been observed in the present study in people without obesity but with recent-onset T2D, with good glycemic control, and in the absence of confounding pharmacological treatment. It is likely that the findings represent a specific marker of T2D, possibly present even in prediabetes before biochemical and clinical manifestations.

Uncovering personalized glucose responses and circadian rhythms from multiple wearable biosensors with Bayesian dynamical modeling

Wearable biosensors and smartphone applications can measure physiological variables over multiple days in free-living conditions. We measure food and drink ingestion, glucose dynamics, physical activity, heart rate (HR), and heart rate variability (HRV) in 25 healthy participants over 14 days. We develop a Bayesian inference framework to learn personal parameters that quantify circadian rhythms and physiological responses to external stressors. Modeling the effects of ingestion events on glucose levels reveals that slower glucose decay kinetics elicit larger postprandial glucose spikes, and we uncover a circadian baseline rhythm for glucose with high amplitudes in some individuals. Physical activity and circadian rhythms explain as much as 40%-65% of the HR variance, whereas the variance explained for HRV is more heterogeneous across individuals. A more complex model incorporating activity, HR, and HRV explains up to 15% of additional glucose variability, highlighting the relevance of integrating multiple biosensors to better predict glucose dynamics.

Reducing Sitting Time in Type 1 Diabetes: Considerations and Implications

Sedentary behaviours are ubiquitous in modern society with Western populations spending approximately ∼50% of their waking hours in low levels of energy expenditure. This behaviour is associated with cardiometabolic derangements and increased morbidity and mortality. In individuals living with or at risk of developing type 2 diabetes (T2D), "breaking up" sedentariness, by interrupting prolonged periods of sitting has been shown to acutely improve glucose control and cardiometabolic risk factors related to diabetes complications. As such, current guidelines recommend interrupting prolonged periods of sitting with short, frequent activity breaks. However, the evidence underpinning these recommendations remain preliminary and are focussed on those with or at risk of developing T2D, with little information regarding whether and how reducing sedentariness may be effective and safe in those living with type 1 diabetes (T1D). In this review, we discuss the potential application of interventions that target prolonged sitting time in T2D within the context of T1D.

Multi-Timescale Rhythmicity of Blood Glucose and Insulin Delivery Reveals Key Advantages of Hybrid Closed Loop Therapy

BACKGROUND

Blood glucose and insulin exhibit coordinated daily and hourly rhythms in people without diabetes (nonT1D). Although the presence and stability of these rhythms are associated with euglycemia, it is unknown if they (1) are preserved in individuals with type 1 diabetes (T1D) and (2) vary by therapy type. In particular, Hybrid Closed Loop (HCL) systems improve glycemia in T1D compared to Sensor Augmented Pump (SAP) therapies, but the extent to which either recapitulates coupled glucose and insulin rhythmicity is not well described. In HCL systems, more rapid modulation of glucose via automated insulin delivery may result in greater rhythmic coordination and euglycemia. Such precision may not be possible in SAP systems. We hypothesized that HCL users would exhibit fewer hyperglycemic event, superior rhythmicity, and coordination relative to SAP users.

METHODS

Wavelet and coherence analyses were used to compare glucose and insulin delivery rate (IDR) within-day and daily rhythms, and their coordination, in 3 datasets: HCL (n = 150), SAP (n = 89), and nonT1D glucose (n = 16).

RESULTS

Glycemia, correlation between normalized glucose and IDR, daily coherence of glucose and IDR, and amplitude of glucose oscillations differed significantly between SAP and HCL users. Daily glucose rhythms differed significantly between SAP, but not HCL, users and nonT1D individuals.

CONCLUSIONS

SAP use is associated with greater hyperglycemia, higher amplitude glucose fluctuations, and a less stably coordinated rhythmic phenotype compared to HCL use. Improvements in glucose and IDR rhythmicity may contribute to the overall effectiveness of HCL systems.

Circadian clock, diurnal glucose metabolic rhythm, and dawn phenomenon

The circadian clock provides cue-independent anticipatory signals for diurnal rhythms of baseline glucose levels and glucose tolerance. The central circadian clock is located in the hypothalamic suprachiasmatic nucleus (SCN), which comprises primarily GABAergic neurons. The SCN clock regulates physiological diurnal rhythms of endogenous glucose production (EGP) and hepatic insulin sensitivity through neurohumoral mechanisms. Disruption of the molecular circadian clock is associated with the extended dawn phenomenon (DP) in type 2 diabetes (T2D), referring to hyperglycemia in the early morning without nocturnal hypoglycemia. The DP affects nearly half of patients with diabetes, with poorly defined etiology and a lack of targeted therapy. Here we review neural and secreted factors in physiological diurnal rhythms of glucose metabolism and their pathological implications for the DP.

Insulin Titration Guidelines for Patients With Type 1 Diabetes: It Is About Time!

PURPOSE

A proposal that an Insulin Advisory Committee develop insulin titration guidelines 100 years after its discovery.

FINDINGS

Glucose control metrics remain poor despite significant advances in diabetes technology.

SUMMARY

A century after the introduction of insulin, health care providers and patients with type 1 diabetes have worldwide access to a variety of insulin delivery devices (IDDs), glucose monitors, bolus calculators (BCs), continuous glucose monitors (CGMs), and automated insulin delivery (AID) systems. However, these advances have not enabled most patients to achieve today's clear A1c and time-in-range goals. Much of this failure arises from the lack of clear insulin titration guidelines for determining appropriate insulin doses. The lack of dosing clarity results in local physicians, clinics, and individual patients managing insulin titrations as they see fit, creating significant inefficiencies for reaching recommended glycemic goals. This review (1) details the widespread problems generated by nonphysiological dose settings in today's BCs, insulin pumps, and AID systems; (2) presents a method to develop and implement optimized total daily doses of insulin to correct the most common problem of hyperglycemia; (3) discusses using large device databases to provide clear insulin titration guidelines that optimize BC settings from an optimized total daily dose (TDD) of insulin for patients with T1D; and (4) recommends the formation of an Insulin Advisory Committee to clarify the steps to take toward universal insulin titration guidelines, optimized BC settings, and a systematic logic for their use in insulin delivery devices.

Sex differences in behavior, response to LPS, and glucose homeostasis in middle-aged mice

Sex and age have distinct influences and roles in behavior and immune reactivity; yet, most studies use adult male rodents with little attention to middle age, a time associated with key physiological transitions in both sexes. Thus, this study investigated sex differences during middle age in behavior, immune response to lipopolysaccharide (LPS), and glucose regulation in C57BL/6 mice with GFP-tagged monocytes/microglia. Behaviorally, males performed better in tests of motor function (Open Field [OF], Grip Strength, Sticker Removal, Gait, and Pole tests) and displayed less depressive- and anxiety-like behaviors across multiple mood tests (OF, Elevated Zero Maze, Sucrose Preference, and Swim test). However, females performed better in tests of cognition (Barnes Maze and Novel Object Recognition). Following behavioral assessment, mice were given LPS to characterize sex-dependent inflammagen responses. Females displayed greater sickness behavior in the OF, higher levels of peripheral cytokines, and subtle neuroinflammation in the cortex, striatum, and hippocampus. A separate middle-aged cohort was used for glucose tolerance and insulin sensitivity testing. Both sexes had excessive blood glucose rebound after insulin challenge, but displayed differences following glucose administration, where males had higher baseline glucose and females remained hyperglycemic. This study suggests that during middle-age male mice have better emotional regulation and motor function, but not cognitive ability than females. Further, males are less sensitive than females to the acute effects of LPS peripherally and centrally, but both sexes showed sex-specific impairments in blood glucose regulation. Overall, it appears that middle age is an important transition point with multiple sex differences, some of which are unique to this stage of life.

Confirmation of the Absence of Somogyi Effect in Patients with Type 2 Diabetes by Retrospective Continuous Glucose Monitoring Systems

BACKGROUND

The Somogyi effect is defined as fasting hyperglycemia secondary to nocturnal hypoglycemia. In past decades, this effect proved to be rare or absent. However, many endocrinologists still believe in this phenomenon in clinical practice. Does the Somogyi effect truly exist? We aimed to answer this question with a study based on a larger sample size.

METHODS

We collected retrospective CGMs data from 2,600 patients with type 2 diabetes with stable treatment of insulin. Nocturnal hypoglycemia was defined as a CGMs sensor glucose of less than 3.9 mmol/L for at least 15 min between 24:00 and 06:00. Morning fasting glucose was compared between people with nocturnal hypoglycemia and without nocturnal hypoglycemia.

RESULTS

Valid CGMs data were obtained on 4,705 of 5,200 nights. Morning fasting glucose was observed lower after nights with nocturnal hypoglycemia compared with nights without hypoglycemia (P < 0.001). 84 cases presented fasting glucose of more than 7 mmol/L after nocturnal glucose of less than 3.9 mmol/L. Only 27 cases presented fasting glucose of more than 7 mmol/L after nocturnal glucose of less than 3.0 mmol/L. Fasting glucose values below 3.9 mmol/l in the morning were associated with a 100% risk of nocturnal hypoglycemia, while fasting glucose values over 9.6 mmol/l in the morning were associated with no risk of nocturnal hypoglycemia. Correlation analysis showed that the nocturnal glucose nadir was significantly correlated with fasting glucose levels (r = 0.613, P < 0.001).

CONCLUSIONS

Our data provided no support for the existence of the Somogyi effect. If fasting glucose exceeds 9.6 mmol/L, we do not have to worry about asymptomatic nocturnal hypoglycemia in patients with type 2 diabetes.

Glucose variability and low bone turnover in people with type 2 diabetes

INTRODUCTION

Type 2 diabetes (T2D) is related to an increased fracture risk and low bone turnover. However, the mechanisms are not elucidated. In the present study we investigate the association between glycemic variability and bone turnover markers.

METHODS

100 participants with T2D and 100 age and gender matched controls were included in this cross-sectional study. All participants with T2D were equipped with a continuous glucose monitoring (CGM) sensor for 3 days (CGMS iPro Continuous Glucose Recorder; Medtronic MiniMed). The dawn glucose levels were defined as a morning period starting 1 h before breakfast ending 1 h post ingestion. On all participants serum (s)-C-terminal cross-linked telopeptide of type-I collagen (CTX), s-procollagen type 1 amino terminal propeptide (P1NP), and s-sclerostin were measured.

RESULTS

Participants with T2D displayed significantly lower levels of the bone resorption marker s-CTX and the bone formation marker s-P1NP compared to controls. S-CTX was significantly negatively associated with the mean amplitude of glycemic excursions (MAGE) and the dawn glucose levels whereas s-P1NP only was significantly negatively associated with the dawn glucose levels while it was borderline significantly associated with MAGE (p = 0.05). S-CTX and s-P1NP were significantly lower among the 50% with the highest dawn glucose levels compared to the 50% lowest dawn glucose levels also after adjustment for age, gender, glycated hemoglobin A1c (HbA1c), and body mass index (BMI).

CONCLUSION

We observed that the amplitude of glycemic excursions and rise in dawn glucose was negatively associated with bone turnover markers. Future research is needed to determine whether reduction of the amplitude of glycemic excursions increase bone turnover markers.

Patients with Type 1 Diabetes Treated with Insulin Pumps Need Widely Heterogeneous Basal Rate Profiles Ranging from Negligible to Pronounced Diurnal Variability

BACKGROUND

Pump-treated patients with type 1 diabetes have widely differing basal insulin infusion profiles. We analyzed consequences of such heterogeneity for glycemic control under fasting conditions.

METHODS

Data from 339 adult patients with type 1 diabetes on insulin pump therapy undergoing a 24-hour fast (basal rate test) were retrospectively analyzed. Hourly programmed basal insulin infusion rates and plasma glucose concentrations as well as their proportions within, below, or above arbitrarily defined target ranges were assessed for specific periods of the day (eg, 1-7 hours, "dawn" period, 16-19 hours, "dusk" period, reference period 20-1 hours/10-14 hours), by tertiles of a predefined "dawn" index (mean basal insulin infusion rate during the "dawn" divided by the reference periods).

RESULTS

The "dawn" index varied interindividually from 0.7 to 4.4. Basal insulin infusion profiles exhibited substantial differences (P = .011), especially overnight. Despite higher insulin infusion rates at 4 and 6.45 hours, patients with the most pronounced "dawn" phenomenon exhibited higher plasma glucose concentrations at those time points (P < .012). Patients with a marked "dawn" phenomenon exhibited a lower probability for low (<4.4 mmol/L) and a higher probability of high values (>7.2 mmol/L) during the dawn period (all P values <.01).

CONCLUSIONS

We observe substantial interindividual heterogeneity in the "dawn" phenomenon. However, widely different empirically derived basal insulin infusion profiles appear appropriate for individual patients, as indicated by similar plasma glucose concentrations, mainly in the target range, during a 24-hour fasting period.

Prediction of Individual Basal Rate Profiles From Patient Characteristics in Type 1 Diabetes on Insulin Pump Therapy

BACKGROUND

Basal rate profiles in patients with type 1 diabetes on insulin pump therapy are subject to enormous inter-individual heterogeneity. Tools to predict basal rates based on clinical characteristics may facilitate insulin pump therapy.

METHODS

Data from 339 consecutive in-patients with adult type 1 diabetes on insulin pump therapy were collected. Basal rate tests were performed over 24 hours. A mathematical algorithm to predict individual basal rate profiles was generated by relating the individual insulin demand to selected clinical characteristics in an exploratory cohort of 170 patients. The predicted insulin pump profiles were validated in a confirmatory cohort of 169 patients.

FINDINGS

Basal rates (0.27 ± 0.01 IU.d^-1.kg^-1) showed circadian variations with peaks corresponding to the "dawn" and "dusk" phenomena. Age, gender, duration of pump treatment, body-mass-index, HbA_1c, and triacylglycerol concentrations largely predicted the individual basal insulin demand per day (IU/d; exploratory vs prospective cohorts: r² = 0.518, P < .0001). Model-predicted and actual basal insulin rates were not different (exploratory cohort: Δ 0.1 (95% CI -0.9; 1.0 U/d; P = .95; prospective cohort: Δ -0.5 (95% CI -1.5; 0.6 IU/d; P = .46). Similarly, precise predictions were possible for each hour of the day. Actual and predicted "dawn" index correlated significantly in the exploratory but not in the confirmatory cohort.

INTERPRETATION

Clinical characteristics predict 52% of the variation in individual basal rate profiles, including their diurnal fluctuations. The multivariate regression model can be used to initiate or optimize insulin pump treatment in patients with type 1 diabetes.

The dawn phenomenon in type 2 diabetes: its association with glucose excursions and changes after oral glucose-lowering drugs

Background:

We investigated the association between glucose excursions and the dawn phenomenon, and the effects of oral-glucose lowering drugs on the dawn phenomenon in patients with type 2 diabetes (T2D).

Methods:

We conducted a post hoc analysis using data from a previous randomized trial. Patients with T2D on metformin monotherapy were randomized to receive add-on acarbose or glibenclamide for 16 weeks. Ambulatory continuous glucose monitoring (CGM) was conducted before randomization and at the end of the study. Using the CGM data, we assessed glucose excursions as indicated by mean amplitude of glycemic excursions (MAGE). The magnitude of the dawn phenomenon was calculated as the difference between the nocturnal nadir (0:00 to 6:00 a.m.) and prebreakfast glucose level.

Results:

A total of 50 patients with T2D [mean age 53.5 ± 8.2 years, mean glycated hemoglobin (HbA1c) 8.4 ± 1.2%] were analyzed. There was an independent association between MAGE and the dawn phenomenon [β coefficient 0.199, 95% confidence interval (CI) 0.074–0.325, p = 0.003]. HbA1c improved significantly after treatment with acarbose or glibenclamide. However, only treatment with acarbose significantly improved glucose excursions. The dawn phenomenon decreased significantly only in patients treated with acarbose (from 35.9 ± 15.7–28.3 ± 16.5 mg/dl, p = 0.037), but not in those treated with glibenclamide (from 35.9 ± 20.6–34.6 ± 17.0 mg/dl, p = 0.776).

Conclusion:

Glucose excursions were independently associated with the dawn phenomenon in patients with T2D on metformin monotherapy. Both glucose excursions and the dawn phenomenon improved after treatment with acarbose, but not after treatment with glibenclamide.

Engineering digital biomarkers of interstitial glucose from noninvasive smartwatches

Prediabetes affects one in three people and has a 10% annual conversion rate to type 2 diabetes without lifestyle or medical interventions. Management of glycemic health is essential to prevent progression to type 2 diabetes. However, there is currently no commercially-available and noninvasive method for monitoring glycemic health to aid in self-management of prediabetes. There is a critical need for innovative, practical strategies to improve monitoring and management of glycemic health. In this study, using a dataset of 25,000 simultaneous interstitial glucose and noninvasive wearable smartwatch measurements, we demonstrated the feasibility of using noninvasive and widely accessible methods, including smartwatches and food logs recorded over 10 days, to continuously detect personalized glucose deviations and to predict the exact interstitial glucose value in real time with up to 84% and 87% accuracy, respectively. We also establish methods for designing variables using data-driven and domain-driven methods from noninvasive wearables toward interstitial glucose prediction.

Epidemiology and outcomes from severe hypoglycemia in Kuwait: a prospective cohort study

Background

The objective of this study was to describe the epidemiology of severe hypoglycaemia in Kuwait, aiming to provide a preliminary background to update the current guidelines and improve patient management.

Method

This was a prospective analysis of severe hypoglycaemia cases retrieved from emergency medical services (EMS) archived data between 1 January and 30 June 2020. The severe hypoglycaemia cases were then sub-grouped based on EMS personal initial management and compared in terms of scene time, transportation rate, complications and outcomes. The primary outcomes were GCS within 10–30 min and normal random blood glucose (RBS) within 10–30 min.

Results

A total of 167 cases met the inclusion criteria. The incidence of severe hypoglycaemia in the national EMS was 11 per 100,000. Intramuscular glucagon was used on scene in 89% of the hypoglycaemic events. Most of the severe hypoglycaemia patients regained normal GCS on scene (76.5%). When we compared the two scene management strategies for severe hypoglycaemia cases, parenteral glucose administration prolonged the on-scene time (P = .002) but was associated with more favourable scene outcomes than intramuscular glucagon, with normal GCS within 10–30 min (P = .05) and normal RBS within 10–30 min (P = .006). Conclusion: Severe hypoglycaemia is not uncommon during EMS calls. Appropriate management by EMS personals is fruitful, resulting in favourable scene outcomes and reducing the hospital transportation rate. More research should be invested in improving and structuring the prehospital management of severe hypoglycaemia. One goal is to clarify the superiority of parenteral glucose over intramuscular glucagon in the prehospital setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-021-00457-9.

The physiological basis of insulin therapy in people with diabetes mellitus

Insulin therapy has been in use now for 100 years, but only recently insulin replacement has been based on physiology. The pancreas secretes insulin at continuously variable rates, finely regulated by sensitive arterial glucose sensing. Pancreatic insulin is delivered directlyin the portal blood to insulinize preferentially the liver. In the fasting state, insulin is secreted at a low rate to modulate hepatic glucose output. After liver extraction (50%), insulin concentrations in peripheral plasma are 2.4-4 times lower than in portal, but still efficacious to restrain lipolysis. In the prandial condition, insulin is secreted rapidly in large amounts to increase portal and peripheral concentrations to peaks 10-20 times greater vs the values of fasting within 30-40 min from meal ingestion. The prandial portal hyperinsulinemia fully suppresses hepatic glucose production while peripheral hyperinsulinemia increases glucose utilization, thus limitating the post-prandial plasma glucose elevation. Physiology of insulin indicates that insulin should be replaced in people with diabetes mimicking the pancreas, i.e. in a basal-bolus mode, for fasting and prandial state, respectively. Despite the presently ongoing limitations (subcutaneous and peripheral rather than portal and intravenous insulin delivery), basal-bolus insulin allows people with diabetes to achieve A1c in the range with minimal risk of hypoglycaemia, to prevent vascular complications and to ensure good quality of life.

A model-based approach to investigating the relationship between glucose-insulin dynamics and dapagliflozin treatment effect in patients with type 2 diabetes

AIMS

To develop a quantitative systems pharmacology model to describe the effect of dapagliflozin (a sodium-glucose co-transporter-2 [SGLT2] inhibitor) on glucose-insulin dynamics in type 2 diabetes mellitus (T2DM) patients, and to identify key determinants of treatment-mediated glycated haemoglobin (HbA1c) reduction.

MATERIALS AND METHODS

Glycaemic control during dapagliflozin treatment was mechanistically characterized by integrating components representing dapagliflozin pharmacokinetics (PK), glucose-insulin homeostasis, renal glucose reabsorption, and HbA1c formation. The model was developed using PK variables, glucose, plasma insulin, and urinary glucose excretion (UGE) from a phase IIa dapagliflozin trial in patients with T2DM (NCT00162305). The model was used to predict dapagliflozin-induced HbA1c reduction; model predictions were compared to actual data from phase III trials (NCT00528879, NCT00683878, NCT00680745 and NCT00673231).

RESULTS

The integrated glucose-insulin-dapagliflozin model successfully described plasma glucose and insulin levels, as well as UGE in response to oral glucose tolerance tests and meal intake. HbA1c reduction was also well predicted. The results show that dapagliflozin-mediated glycaemic control is anticorrelated to steady-state insulin concentration and insulin sensitivity.

CONCLUSIONS

The developed model framework is the first to integrate SGLT2 inhibitor mechanism of action with both short-term glucose-insulin dynamics and long-term glucose control (HbA1c). The results suggest that dapagliflozin treatment is beneficial in patients with inadequate glycaemic control from insulin alone and this benefit increases as insulin control diminishes.

REV-ERB in GABAergic neurons controls diurnal hepatic insulin sensitivity

Systemic insulin sensitivity shows a diurnal rhythm with a peak upon waking1,2. The molecular mechanism that underlies this temporal pattern is unclear. Here we show that the nuclear receptors REV-ERB-α and REV-ERB-β (referred to here as 'REV-ERB') in the GABAergic (γ-aminobutyric acid-producing) neurons in the suprachiasmatic nucleus (SCN) (SCNGABA neurons) control the diurnal rhythm of insulin-mediated suppression of hepatic glucose production in mice, without affecting diurnal eating or locomotor behaviours during regular light-dark cycles. REV-ERB regulates the rhythmic expression of genes that are involved in neurotransmission in the SCN, and modulates the oscillatory firing activity of SCNGABA neurons. Chemogenetic stimulation of SCNGABA neurons at waking leads to glucose intolerance, whereas restoration of the temporal pattern of either SCNGABA neuron firing or REV-ERB expression rescues the time-dependent glucose metabolic phenotype caused by REV-ERB depletion. In individuals with diabetes, an increased level of blood glucose after waking is a defining feature of the 'extended dawn phenomenon'3,4. Patients with type 2 diabetes with the extended dawn phenomenon exhibit a differential temporal pattern of expression of REV-ERB genes compared to patients with type 2 diabetes who do not have the extended dawn phenomenon. These findings provide mechanistic insights into how the central circadian clock regulates the diurnal rhythm of hepatic insulin sensitivity, with implications for our understanding of the extended dawn phenomenon in type 2 diabetes.

Twenty-Four Hour Fasting (Basal Rate) Tests to Achieve Custom-Tailored, Hour-by-Hour Basal Insulin Infusion Rates in Patients With Type 1 Diabetes Using Insulin Pumps (CSII)

BACKGROUND

Twenty-four hour fasting periods are being used to scrutinize basal insulin infusion rates for pump-treated patients with type 1 diabetes.

METHODS

Data from 339 consecutive in-patients with adult type 1 diabetes on insulin pump therapy undergoing a 24-hour fast as a basal rate test were retrospectively analyzed. Hourly programmed basal insulin infusion rates and plasma glucose concentrations within, below, or above arbitrarily defined target ranges were assessed for periods of the day of special interest (eg, 01:00-07:00 am, "dawn" period, 04:00-07:00 pm, and "dusk" period). Statistics: χ²-tests, paired t-tests were used.

RESULTS

Basal rates (mean: 0.90 ± 0.02 IU/h) showed circadian variations with peaks corresponding to "dawn" (1.07 ± 0.02 IU/h from 01:00 to 07:00 am) and, less prominently, "dusk" (0.95 ± 0.02 IU/h from 03:00 to 07:00 pm). Individual mean plasma glucose concentrations averaged 6.6 ± 0.1 mmol/L, with 53.1% in the predefined "strict" (4.4-7.2 mmol/L) target range. Interestingly, during the "dawn" period, plasma glucose was significantly higher (by 0.5 ± 0.1 mmol/L [95% confidence interval: 0.3-0.8 mmol/L; P < .0001]) and the odds ratio for hypoglycemia was significantly lower compared to the reference period.

INTERPRETATION

Twenty-four hour fasting periods as basal rate tests frequently unravel periods with inappropriate basal insulin infusion rates potentially responsible for fasting hyper- or hypoglycemia. Notably, the higher basal insulin infusion rate found during the "dawn" period seems to be justified and may need to be accentuated.

The dawn phenomenon across the glycemic continuum: Implications for defining dysglycemia

AIMS

To investigate the frequency of dawn phenomenon (DP) and its relationship with time in range (TIR) and glycemic variability (GV) using continuous glucose monitoring (CGM).

METHODS

781 subjects of a multicenter CGM study in China were included: those with normal glucose tolerance (NGT n = 360); impaired glucose regulation (IGR n = 173); newly diagnosed type 2 diabetes mellitus (T2D n = 248). Analysis of the magnitude of DP (ΔG) was conducted with the primary definition of 1.11 mmol/L and a secondary definition of 0.56 mmol/L.

RESULTS

The frequency of DP was 8.9%, 30.1% and 52.4% in NGT, IGR and T2D group, respectively, using the primary definition. In all three groups, TIR was lower (all P < 0.05), coefficient of variation (CV) was higher in DP subgroup (all P < 0.05). In DP subgroup of T2D, TIR was 7.0% (1.68 h) lower and CV was 3.0% higher, and HbA_1c was 0.6% (7 mmol/mol) higher using the primary definition (all P < 0.05).

CONCLUSIONS

DP was present in a high percent of subjects with NGT and IGR. In newly diagnosed T2D group, the presence of DP was associated with poorer overall glycemic control.

Long-term glycemic control and prevention of diabetes complications in vivo using oleic acid-grafted-chitosan‑zinc-insulin complexes incorporated in thermosensitive copolymer

Daily injections for basal insulin therapy are far from ideal resulting in hypo/hyperglycemic episodes associated with fatal complications in type-1 diabetes patients. Here we report a delivery system that provides controlled release of insulin closely mimicking physiological basal insulin requirement for an extended period following a single subcutaneous injection. Stability of insulin was significantly improved by formation of zinc-insulin hexamers, further stabilized by electrostatic complex formation with chitosan polymer. Insulin complexes were homogenously incorporated into PLA-PEG-PLA, a biodegradable thermogel copolymer, that instantaneously forms a subcutaneous gel-depot following injection. Chitosan polymer was hydrophobically modified using oleic acid prior to complex formation with insulin to enable distribution of oleic acid-grafted-chitosan‑zinc-insulin complexes into the hydrophobic core of PLA-PEG-PLA thermogel-copolymer micelles. In vivo, daily administration of marketed long-acting insulin, glargine, resulted in fluctuating blood glucose levels between 91 and 443 mg/dL in type 1 diabetic rats. However, single administration of thermogel copolymeric formulation successfully demonstrated slow diffusion of insulin complexes maintaining peak-free basal insulin level of 21 mU/L for 91 days. Sustained release of basal insulin also correlated with efficient glycemic control (blood glucose <120 mg/dL), prevention of diabetic ketoacidosis and absence of cataract development, unlike other treatment groups. Moreover, there was no sign of inflammation, tissue damage, or collagen deposition around depot site, suggesting exceptional biocompatibility of the formulation for long-term use.

Review of methods for detecting glycemic disorders

Prediabetes (intermediate hyperglycemia) consists of two abnormalities, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) detected by a standardized 75-gram oral glucose tolerance test (OGTT). Individuals with isolated IGT or combined IFG and IGT have increased risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). Diagnosing prediabetes early and accurately is critical in order to refer high-risk individuals for intensive lifestyle modification. However, there is currently no international consensus for diagnosing prediabetes with HbA1c or glucose measurements based upon American Diabetes Association (ADA) and the World Health Organization (WHO) criteria that identify different populations at risk for progressing to diabetes. Various caveats affecting the accuracy of interpreting the HbA1c including genetics complicate this further. This review describes established methods for detecting glucose disorders based upon glucose and HbA1c parameters as well as novel approaches including the 1-hour plasma glucose (1-h PG), glucose challenge test (GCT), shape of the glucose curve, genetics, continuous glucose monitoring (CGM), measures of insulin secretion and sensitivity, metabolomics, and ancillary tools such as fructosamine, glycated albumin (GA), 1,5- anhydroglucitol (1,5-AG). Of the approaches considered, the 1-h PG has considerable potential as a biomarker for detecting glucose disorders if confirmed by additional data including health economic analysis. Whether the 1-h OGTT is superior to genetics and omics in providing greater precision for individualized treatment requires further investigation. These methods will need to demonstrate substantially superiority to simpler tools for detecting glucose disorders to justify their cost and complexity.

Modeling continuous glucose monitoring (CGM) data during sleep

We introduce a multilevel functional Beta model to quantify the blood glucose levels measured by continuous glucose monitors for multiple days in study participants with type 2 diabetes mellitus. The model estimates the subject-specific marginal quantiles, quantifies the within- and between-subject variability, and produces interpretable parameters of blood glucose dynamics as a function of time from the actigraphy-estimated sleep onset. Results are validated via simulations and by studying the association between the estimated model parameters and hemoglobin A1c, the gold standard for assessing glucose control in diabetes.

The continuing quest for better subcutaneously administered prandial insulins: a review of recent developments and potential clinical implications

The class of rapid-acting insulin analogues were introduced more than 20 years ago to control postprandial plasma glucose (PPG) excursions better than unmodified regular human insulin. Insulins, lispro, aspart and glulisine all achieved an earlier onset of action, greater peak effect and shorter duration of action resulting in lower PPG levels and a reduced risk of late postprandial hypoglycaemia. However, the subcutaneous absorption rate of these analogues still fails to match the physiological profile of insulin in the systemic circulation following a meal. Recent reformulations of aspart and lispro have generated a second generation of more rapid-acting insulin analogue candidates, including fast-acting aspart (faster aspart), ultra-rapid lispro and BioChaperone Lispro. These modifications have the potential to mimic physiological prandial insulin secretion better with an even earlier onset of action with improved PPG control, shorter duration of effect and reduced risk of hypoglycaemia. Recent phase 3 trials in type 1 and type 2 diabetes show that faster aspart and ultra-rapid lispro compared with conventional aspart and lispro, achieved fewer PPG excursions with a small increase in post-meal hypoglycaemia but similar or marginally superior glycated haemoglobin levels, and suggest the need for parallel optimization of basal insulin replacement. Phase 1 trials for BioChaperone Lispro are equally encouraging with phase 3 trials yet to be initiated. Comparative analysis of the clinical and pharmacological evidence for these new prandial insulin candidates in the treatment of type 1 and type 2 diabetes is the main focus of this review.

Effects of Exercise on Blood Glucose and Glycemic Variability in Type 2 Diabetic Patients with Dawn Phenomenon

Background

The dawn phenomenon (DP) is the primary cause of difficulty in blood glucose management in type 2 diabetic (T2D) patients, and the use of oral hypoglycemic agents has shown weak efficacy in controlling DP. Thus, this study is aimed at investigating the effect of moderate-intensity aerobic exercise before breakfast on the blood glucose level and glycemic variability in T2D patients with DP.

Methods

A total of 20 T2D patients with DP confirmed via continuous glucose monitoring (CGM) participated in the current study. After collecting baseline measurements by CGM as a control, CGM was reinstalled and 30 minutes of moderate-intensity aerobic exercise was performed prior to breakfast. Dawn blood glucose increase, blood glucose levels, and glycemic variability were measured before and after exercise.

Results

Dawn blood glucose increase (ΔGlu, 1.25 ± 0.84vs.2.15 ± 1.07, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs. 8.78 ± 1.09, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs. 8.78 ± 1.09, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs. 8.78 ± 1.09, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs. 8.78 ± 1.09, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs.2.15 ± 1.07, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs.2.15 ± 1.07, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16vs.2.15 ± 1.07, P = 0.005), highest blood glucose value before breakfast (Gmax, 8.01 ± 1.16

Conclusions

Acute moderate-intensity aerobic exercise before breakfast reduced the morning rise of blood glucose in T2D patients, partially counteracting DP. Furthermore, exercise significantly reduced blood glucose fluctuations and improved blood glucose control throughout the day. We recommend that T2D patients with DP take moderate-intensity aerobic exercise before breakfast to improve DP and glycemic control.

Insulin Therapy in Adults with Type 1 Diabetes Mellitus: a Narrative Review

Here, we review insulin management options and strategies in nonpregnant adult patients with type 1 diabetes mellitus (T1DM). Most patients with T1DM should follow a regimen of multiple daily injections of basal/bolus insulin, but those not meeting individual glycemic targets or those with frequent or severe hypoglycemia or pronounced dawn phenomenon should consider continuous subcutaneous insulin infusion. The latter treatment modality could also be an alternative based on patient preferences and availability of reimbursement. Continuous glucose monitoring may improve glycemic control irrespective of treatment regimen. A glycemic target of glycated hemoglobin < 7% (53 mmol/mol) is appropriate for most nonpregnant adults. Basal insulin analogues with a reduced peak profile and an extended duration of action with lower intraindividual variability relative to neutral protamine Hagedorn insulin are preferred. The clinical advantages of basal analogues compared with older basal insulins include reduced injection burden, better efficacy, lower risk of hypoglycemic episodes (especially nocturnal), and reduced weight gain. For prandial glycemic control, any rapid-acting prandial analogue (aspart, glulisine, lispro) is preferred over regular human insulin. Faster-acting insulin aspart is a relatively new option with the advantage of better postprandial glucose coverage. Frequent blood glucose measurements along with patient education on insulin dosing based on carbohydrate counting, premeal blood glucose, and anticipated physical activity is paramount, as is education on the management of blood glucose under different circumstances.Plain Language Summary: Plain language summary is available for this article.

Analysis of Prevalence, Magnitude and Timing of the Dawn Phenomenon in Adults and Adolescents With Type 1 Diabetes: Descriptive Analysis of 2 Insulin Pump Trials

OBJECTIVES

To better understand the dawn phenomenon in type 1 diabetes, we sought to determine its prevalence, timing and magnitude in studies specifically designed to assess basal insulin requirements in patients using insulin pumps.

METHODS

Thirty-three participants from 2 sensor-augmented insulin pump studies were analyzed. Twenty participants were obtained from a methodologically ideal semiautomated basal analysis trial in which basal rates were determined from repeated fasting tests (the derivation set) and 13 from an artificial pancreas trial in which duration of fasting was variable (the "confirmation" set). Prevalence was determined for the total cohort and for individual trials using the standard definition of an increase in insulin exceeding 20% and lasting ≥90 minutes. Among cases, time of onset and percent change in the magnitude of basal delivery were determined.

RESULTS

Seventeen participants (52%) experienced the dawn phenomenon (11 of 20 [55%] in the derivation set and 6 of 13 [46%] in the confirmation set). Time of onset was 3 AM (interquartile range [IQR], 3 to 4:15 AM) in the derivation set and 3 AM (IQR, 3 to 4 AM) in the confirmation set. The magnitude of the dawn phenomenon was a 58.1% (IQR, 28.8% to 110.6%) increase in insulin requirements in the derivation set and 65.5% (IQR, 45.6% to 87.4%) in the confirmation set.

CONCLUSIONS

The dawn phenomenon occurs in approximately half of patients with type 1 diabetes; when present, it has predictable timing of onset (generally 3 AM) and a substantial, but highly variable, magnitude. These findings imply that optimization of glycemic control requires clinical emphasis on fasted overnight basal insulin assessment.

Dose-response between frequency of interruption of sedentary time and fasting glucose, the dawn phenomenon and night-time glucose in Type 2 diabetes

AIM

To explore the dose-response between frequency of interruption of sedentary time and basal glucose (fasting glucose, the dawn phenomenon and night-time glucose) in Type 2 diabetes.

METHODS

In a randomized three-treatment, two-period balanced incomplete block trial, 12 people with Type 2 diabetes (age, 60.0 ± 3.2 years; BMI, 30.2 ± 1.4 kg/m² ) completed two of three conditions: sitting for 7 h interrupted every 60 min (Condition 1), 30 min (Condition 2), and 15 min (Condition 3) by 3-min light-intensity walking breaks. The activPAL3 and FreeStyle Libre were used to assess physical activity/sedentary behaviour and continuous glucose profile. Standardized meals were provided, and changes in basal glucose of the nights and early mornings before and after treatment conditions were calculated (mean ± SE).

RESULTS

After treatment conditions, fasting glucose and duration of the dawn phenomenon were lower for Condition 3 (-1.0 ± 0.2 mmol/l, P < 0.02; -3.1 ± 1.3 h, P = 0.004) compared with Condition 1 (-0.1 ± 0.2 mmol/l; 1.9 ± 1.2 h). The magnitude of the dawn phenomenon was reduced in Condition 3 (-0.6 ± 0.4 mmol/l, P = 0.041) compared with Condition 2 (0.6 ± 0.3 mmol/l). Night-time glycaemic variability (coefficient of variation) was reduced in Condition 3 (-9.7 ± 3.9%) relative to Condition 2 (6.1 ± 4.8%, P < 0.03) and Condition 1 (2.5 ± 1.8%, P = 0.02). There was no change in night-time mean glucose.

CONCLUSIONS

Frequent interruptions of prolonged sitting with 3 min of light-intensity walking breaks every 15 min improves fasting glucose, the dawn phenomenon and night-time glycaemic variability, and this might be a simple therapeutic intervention to improve glucose control. Clinicaltrials.gov Identifier: NCT02738996.

A Slow-Digesting, Low-Glycemic Load Nutritional Beverage Improves Glucose Tolerance in Obese Pregnant Women Without Gestational Diabetes

BACKGROUND

Obesity is a risk factor for gestational diabetes (gestational diabetes). Low-glycemic index diets attenuate hyperglycemia. We designed a study to determine whether a slow-digesting, low-glycemic load (SD-LGL) beverage improves glucose tolerance in obese pregnant women without GDM.

METHODS

This was a 3-arm comparison study comparing the effects of an SD-LGL nutritional beverage (glycemic load [GL] 730), an isocaloric control beverage (GL 1124), and habitual diet on glycemia in obese pregnant women. Sixteen women (mean body mass index 37 kg/m²) were recruited at 24-28 weeks to receive either the SD-LGL or eucaloric control beverage. This was consumed with breakfast and as a midafternoon snack over 2 days with a controlled diet. Following a 2-day washout period of habitual diet, women completed 2 days on the alternative beverage with controlled diet. A 10-h fast preceded each intervention phase. Twenty-four hour glucose was measured using continuous glucose monitoring.

RESULTS

Consumption of the lower GL beverage was associated with improved measures of glycemia, compared with the control beverage and habitual diet at different time periods. Glucose estimates for control versus SD-LDL at 24 h (0.23 mmol/L [0.16 to 0.31], P < 0.001), daytime (0.26 mmol/L [0.18 to 0.34], P < 0.001), and nighttime (0.05 mmol/L [-0.01 to 0.11], P = 0.09). Postprandial glucose was lower after breakfast but not after dinner, compared with the control beverage (0.09 mmol/L [0.01 to 0.18], P = 0.03).

CONCLUSION

A slow-digesting, low-glycemic nutritional beverage may facilitate improved glucose control in obese pregnant women. To address potential benefit for clinical outcomes, a randomized controlled trial is warranted.

Clinical diagnosis for dusk phenomenon of diabetes

The diabetes dusk phenomenon (spontaneous and transient pre-dinner hyperglycemia) anecdotally exists but has not been investigated.A total of 80 diabetic patients that received continuous subcutaneous insulin infusions were retrospectively studied. They were grouped into a routine group (R) (consecutive δDG [dusk blood glucose difference] <0 mmol/L) and a classic dusk phenomenon group (CDP, consecutive δDG≥0 mmol/L). δDG represents differences in blood glucose measurements between pre-dinner and post-lunch (δDG: dusk blood glucose difference). Other patients were placed in a suspicious group (S). The suspicious group was further divided into 3 groups based on the frequency at which the δDG occurred: suspicious 1 group (S1), δDG≥0 mmol/L occurred once only; suspicious 3 group (S3), δDG < 0 mmol/L occurred once only, and the remaining patients were grouped in the suspicious 2 group (S2).We identified the CDP and S3 groups as the "clinical dusk phenomenon" group (CLDP). We confirmed that the S1 and R groups to be in the "clinical routine" group. The S2 group was significantly different from the CDP group. In addition, the S2 group had significant differences in δDG measurements and post-lunch blood glucose values compared with the R group, but no differences in other parameters were seen. Multiple comparisons with the other suspicious groups also showed no statistical difference in many parameters. Thus, we placed these patients into the "suspicious clinical dusk phenomenon" group (SDP). The δDG cut-off for the CLDP group was 1.0167 mmol/L. The pre-dinner-pre-lunch blood glucose cut-off for this group was 2.72 mmol/L. The δDG cut-off for the SDP group was -0.95 mmol/L. The pre-dinner-pre-lunch blood glucose cut-off for this group was 0.87 mmol/L. The cut-off points for the post-dinner-post-lunch blood glucose measurements in the CLDP and SDP groups were both 1.2667 mmol/L.A consecutive δDG≥0 or a once only δDG < 0 could be diagnosed as falling into the CLDP group. The CLDP could be excluded when a consecutive δDG < 0 or a once only δDG≥0 was found. Patients falling into other categories were placed into the SDP group.

Severe fasting hypoglycemia in a child after total pancreatectomy with islet autotransplantation

TPIAT is an increasingly utilized treatment option for select children with CP. Post-TPIAT fasting hypoglycemia, unrelated to exogenous insulin, is a complication recently reported in adults. This phenomenon has not been described in children. We review a case of severe fasting hypoglycemia in an adolescent female occurring 10 months post-TPIAT. A 12-year-old girl underwent TPIAT for CP. Ten months postoperatively she developed recurrent hypoglycemia on a total daily insulin dose of 0.03 units/kg. Consequently, insulin therapy was discontinued. Approximately 20 hours after her last rapid-acting insulin exposure, she had an episode of fasting hypoglycemia (33 mg/dL on glucometer). Her CGM documented two separate, precipitous drops in glucose overnight. The family was instructed to revise her diet, and there were no subsequent episodes of severe, fasting hypoglycemia. This is the first report of fasting hypoglycemia occurring post-TPIAT in a pediatric patient. Use of a CGM allowed for documentation of glucose trends and alarm notification of hypoglycemic events. Dietary changes appeared to help mitigate hypoglycemia recurrence. This report demonstrates that fasting hypoglycemia is a potential complication that should be recognized and safeguarded against in post-TPIAT pediatric patients.

Dietary Supplement of Large Yellow Tea Ameliorates Metabolic Syndrome and Attenuates Hepatic Steatosis in db/db Mice

Yellow tea has been widely recognized for its health benefits. However, its effects and mechanism are largely unknown. The current study investigated the mechanism of dietary supplements of large yellow tea and its effects on metabolic syndrome and the hepatic steatosis in male db/db mice. Our data showed that dietary supplements of large yellow tea and water extract significantly reduced water intake and food consumption, lowered the serum total and low-density lipoprotein cholesterol and triglyceride levels, and significantly reduced blood glucose level and increased glucose tolerance in db/db mice when compared to untreated db/db mice. In addition, the dietary supplement of large yellow tea prevented the fatty liver formation and restored the normal hepatic structure of db/db mice. Furthermore, the dietary supplement of large yellow tea obviously reduced the lipid synthesis related to gene fatty acid synthase, the sterol regulatory element-binding transcription factor 1 and acetyl-CoA carboxylase α, as well as fatty acid synthase and sterol response element-binding protein 1 expression, while the lipid catabolic genes were not altered in the liver of db/db mice. This study substantiated that the dietary supplement of large yellow tea has potential as a food additive for ameliorating type 2 diabetes-associated symptoms.

Switching basal insulins in type 2 diabetes: practical recommendations for health care providers

Basal insulin remains the mainstay of treatment of type 2 diabetes when diet changes and exercise in combination with oral drugs and other injectable agents are not sufficient to control hyperglycemia. Insulin therapy should be individualized, and several factors influence the choice of basal insulin; these include pharmacological properties, patient preferences, and lifestyle, as well as health insurance plan formularies. The recent availability of basal insulin formulations with longer durations of action has provided further dosing flexibility; however, patients may need to switch agents throughout therapy for a variety of personal, clinical, or economic reasons. Although a unit-to-unit switching approach is usually recommended, this conversion strategy may not be appropriate for all patients and types of insulin. Glycemic control and risk of hypoglycemia must be closely monitored by health care providers during the switching process. In addition, individual changes in care and formulary coverage need to be adequately addressed in order to enable a smooth transition with optimal outcomes.

Features of continuous glycemic profile and glycemic variability in patients with obstructive sleep apnea syndrome

AIMS

To investigate glycemic variability (GV) in Obstructive Sleep Apnea Syndrome (OSAS) patients by monitoring continuous blood glucose profile.

METHODS

OSAS group (n=86) and normal control group (n=40) were included. Continuous blood glucose was monitored. The relationship of GV, insulin resistance index (IRI) and the respiratory disturbance index (AHI) were analyzed.

RESULTS

The daily average blood glucose level was significantly higher in the OSAS patients than in the control group (6.31±0.61vs. 4.94±0.78; P<0.01). The postprandial glycemic peaks in the OSAS patients were significantly higher and prolonged. The indicators of GV were all significantly higher in the OSAS patients, including blood glucose fluctuation coefficient (BGFC, 1.93±0.71vs. 1.21±0.38, P<0.05), mean amplitude of glycemic excursions (MAGE, 4.18±0.65vs. 2.18±0.48; P<0.05) and night mean amplitude of glycemic excursions (NMAGE, 2.00±0.53vs. 1.11±0.43; P<0.05). Pearson correlation analysis showed that among the OSAS patients, the severity of OSAS (AHI) was positively correlated with the IRI (r=0.310); and the GV indicators (MAGE and NMAGE) were positively correlated with IRI and AHI (r=0.318 and 0.349, respectively) (P<0.01 or 0.001).

CONCLUSIONS

Continuous glycemic spectrum and GV provide comprehensive glycemic profiles and may reveal important aspects of glucose metabolism abnormality beyond regular examinations, and are therefore of particular significance for glycemic management in OSAS patients.

Long-term blood glucose monitoring with implanted telemetry device in conscious and stress-free cynomolgus monkeys

AIMS

Continuous blood glucose monitoring, especially long-term and remote, in diabetic patients or research is very challenging. Nonhuman primate (NHP) is an excellent model for metabolic research, because NHPs can naturally develop Type 2 diabetes mellitus (T2DM) similarly to humans. This study was to investigate blood glucose changes in conscious, moving-free cynomolgus monkeys (Macaca fascicularis) during circadian, meal, stress and drug exposure.

MATERIALS AND METHODS

Blood glucose, body temperature and physical activities were continuously and simultaneously recorded by implanted HD-XG telemetry device for up to 10 weeks.

RESULTS AND DISCUSSION

Blood glucose circadian changes in normoglycemic monkeys significantly differed from that in diabetic animals. Postprandial glucose increase was more obvious after afternoon feeding. Moving a monkey from its housing cage to monkey chair increased blood glucose by 30% in both normoglycemic and diabetic monkeys. Such increase in blood glucose declined to the pre-procedure level in 30 min in normoglycemic animals and >2 h in diabetic monkeys. Oral gavage procedure alone caused hyperglycemia in both normoglycemic and diabetic monkeys. Intravenous injection with the stress hormones, angiotensin II (2 μg/kg) or norepinephrine (0.4 μg/kg), also increased blood glucose level by 30%. The glucose levels measured by the telemetry system correlated significantly well with glucometer readings during glucose tolerance tests (ivGTT or oGTT), insulin tolerance test (ITT), graded glucose infusion (GGI) and clamp.

CONCLUSION

Our data demonstrate that the real-time telemetry method is reliable for monitoring blood glucose remotely and continuously in conscious, stress-free, and moving-free NHPs with the advantages highly valuable to diabetes research and drug discovery.

Effect of one week of CPAP treatment of obstructive sleep apnoea on 24-hour profiles of glucose, insulin and counter-regulatory hormones in type 2 diabetes

Studies examining the impact of CPAP treatment on glycaemic control have yielded conflicting results, partly because of insufficient nightly CPAP use. We examined the 24-hour profiles of glucose, insulin and counter-regulatory hormones in 12 subjects with type 2 diabetes and OSA before and after 1 week of effective in-laboratory CPAP therapy over an entire 8-hour night thus ensuring optimal CPAP compliance. Blood samples were collected every 15 to 30 minutes for 24 hours under controlled conditions. The 24-hour mean glucose decreased from 153.2 ± 33.0 to 139.7 ± 24.2 mg/dL with CPAP (-13.5 ± 13.5 mg/dL; P = .005) without change in insulin levels. Morning fasting glucose levels decreased by 14.6 ± 3 mg/dL (P = .001) and the dawn phenomenon decreased by 7.8 ± 9.8 mg/dL (P = .019). CPAP treatment decreased norepinephrine levels while the 24-hour profiles of growth hormone and cortisol remained unchanged. In conclusion, 1 week of effective treatment of OSA over an entire 8-hour night results in a clinically significant improvement in glycaemic control via an amelioration of evening fasting glucose metabolism and a reduction in the dawn phenomenon, a late-night glucose increase that is not adequately treated by oral medications. Clinical Trials Information: ClinicalTrials.gov Identifier: NCT01136785.

Views and Experiences of New Zealand Women with Gestational Diabetes in Achieving Glycaemic Control Targets: The Views Study

INTRODUCTION

Optimal glycaemic control in women with gestational diabetes mellitus (GDM) reduces maternal and infant morbidity.

METHOD

A survey was administered to women diagnosed with GDM to explore their views and experiences in achieving optimal glycaemic control.

RESULTS

Sixty women participated. Enablers included being taught to test capillary blood glucose in group settings where the health professional demonstrated this on themselves first (60, 100%); health professionals listening (41, 68%); being reminded to perform blood glucose testing (33, 55%); and being provided healthy meals by friends and family (28, 47%). Barriers included not having information in a woman's first language (33, 55%); being offered unhealthy food (19, 31%); not being believed by health professionals (13, 21%); receiving inconsistent information by health professionals (10, 16%); never being seen twice by the same health professional (8, 13%); and long waiting hours at clinics (7, 11%). Two-thirds of women (37, 62%) reported that food costs were not a barrier, but that they were always or frequently hungry.

CONCLUSION

Optimising experiences for women with GDM for achieving glycaemic control and overcoming barriers, regardless of glycaemic targets, requires further focus on providing meaningful health literacy and support from health professionals, family, friends, and work colleagues.

Self-Monitoring of Blood Glucose to Assess Dawn Phenomenon in Chinese People with Type 2 Diabetes Mellitus

Aims. We investigated whether self-monitoring of blood glucose could be used to assess dawn phenomenon in Chinese people with type 2 diabetes mellitus (T2DM). Methods. A total of 306 people with T2DM underwent continuous glucose monitoring and self-monitoring of blood glucose for 72 h. A linear model was used to fit the optimal linear formula of the magnitude of dawn phenomenon (ΔDawn) and self-monitoring of blood glucose values. Results. The prevalence of dawn phenomenon was similar within different oral antidiabetic drug groups (42.5%, 31.5%, and 40.9%, P = 0.216). Multiple variable linear regression showed that prebreakfast, prelunch, and predinner glucose measurements were independently and significantly correlated with ΔDawn. The linear formula between ΔDawn and blood glucose was as follows: ΔDawn (mg/dL) = 0.557 × prebreakfast - 0.065 × prelunch - 0.164 × predinner - 20.894 (mg/dL) (adjusted R² = 0.302, P = 0.000). Conclusions. Dawn phenomenon could be partly assessed by blood glucose self-monitoring in Chinese people with T2DM using the abovementioned formula. The incidence of dawn phenomenon was similar among patients in different oral antidiabetic drug groups.

Poor Sleep Quality Is Associated with Dawn Phenomenon and Impaired Circadian Clock Gene Expression in Subjects with Type 2 Diabetes Mellitus

Aims. We investigated whether poor sleep quality is associated with both dawn phenomenon and impaired circadian clock gene expression in subjects with diabetes. Methods. 81 subjects with diabetes on continuous glucose monitoring were divided into two groups according to the Pittsburgh Sleep Quality Index. The magnitude of dawn phenomenon was quantified by its increment from nocturnal nadir to prebreakfast. Peripheral leucocytes were sampled from 81 subjects with diabetes and 28 normal controls at 09:00. Transcript levels of circadian clock genes (BMAL1, PER1, PER2, and PER3) were determined by real-time quantitative polymerase chain reaction. Results. The levels of HbA1c and fasting glucose and the magnitude of dawn phenomenon were significantly higher in the diabetes group with poor sleep quality than that with good sleep quality. Peripheral leucocytes from subjects with poor sleep quality expressed significantly lower transcript levels of BMAL1 and PER1 compared with those with good sleep quality. Poor sleep quality was significantly correlated with magnitude of dawn phenomenon. Multiple linear regression showed that sleep quality and PER1 were significantly independently correlated with dawn phenomenon. Conclusions. Dawn phenomenon is associated with sleep quality. Furthermore, mRNA expression of circadian clock genes is dampened in peripheral leucocytes of subjects with poor sleep quality.

Spontaneous and transient predinner hyperglycemia in some patients with diabetes: Dusk phenomenon

Blood glucose fluctuations have higher risk than absolute blood glucose level in diabetic chronic complications. At present, "dawn phenomenon" is well known by clinicians, but "dusk phenomenon" has not been recognized. This study explored the objective existence of "dusk phenomenon" (spontaneous and transient predinner hyperglycemia) and its clinical significance.The data of 54 patients with diabetes, who received routine insulin pump therapy between December 2010 and October 2012 in our hospital, were retrospectively analyzed. These patients included 4 patients with type 1 diabetes mellitus (DM) (T1DM) and 50 patients with type 2 DM (T2DM). According to the difference between predinner and postlunch blood glucose levels, the 50 patients with T2DM were divided into dusk phenomenon group (4 patients, all the differences ≥0 mmol/L during insulin pump therapy), nondusk phenomenon group (12 patients, all the differences <0 mmol/L during insulin pump therapy), and suspicious group (34 patients, the differences were uncertain during insulin pump therapy). In the 4 patients with T1DM of this study, the differences all were more than 0 mmol/L during insulin pump therapy. The changes in blood glucose levels were observed, and the correlations of blood glucose level with other factors were analyzed in T1DM and T2DM patients, respectively.In T1DM patients, blood glucose level was significantly higher in predinner than in prebreakfast and prelunch (all P < 0.01), and in postdinner 2 hour than in postlunch 2 hour (P = 0.021). The predinner blood level had no significant correlations with the blood glucose level at other time points and insulin dosages (all P > 0.05). In T2DM patients, the predinner blood glucose level was significantly higher in dusk phenomenon group than in suspicious group and nondusk phenomenon group (all P < 0.05). In dusk phenomenon group, the blood glucose level remained rising from predinner to prebed, and the predinner blood glucose level was only significantly correlated with postdinner 2-hour blood glucose level (P < 0.05).The "dusk phenomenon" (spontaneous and transient predinner hyperglycemia) is an objective existence in some patients with diabetes. The predinner hyperglycemia can affect blood glucose control between postdinner and prebed. Awareness of the "dusk phenomenon" has important clinical significance.

Enhanced Model Predictive Control (eMPC) Strategy for Automated Glucose Control

Development of an effective artificial pancreas (AP) controller to deliver insulin autonomously to people with type 1 diabetes mellitus is a difficult task. In this paper, three enhancements to a clinically validated AP model predictive controller (MPC) are proposed that address major challenges facing automated blood glucose control, and are then evaluated by both in silico tests and clinical trials. First, the core model of insulin-blood glucose dynamics utilized in the MPC is expanded with a medically inspired personalization scheme to improve controller responses in the face of inter- and intra-individual variations in insulin sensitivity. Next, the asymmetric nature of the short-term consequences of hypoglycemia versus hyperglycemia is incorporated in an asymmetric weighting of the MPC cost function. Finally, an enhanced dynamic insulin-on-board algorithm is proposed to minimize the likelihood of controller-induced hypoglycemia following a rapid rise of blood glucose due to rescue carbohydrate load with accompanying insulin suspension. Each advancement is evaluated separately and in unison through in silico trials based on a new clinical protocol, which incorporates induced hyper- and hypoglycemia to test robustness. The advancements are also evaluated in an advisory mode (simulated) testing of clinical data. The combination of the three proposed advancements show statistically significantly improved performance over the nonpersonalized controller without any enhancements across all metrics, displaying increased time in the 70-180 mg/dL safe glycemic range (76.9 versus 68.8%) and the 80-140 mg/dL euglycemic range (48.1 versus 44.5%), without a statistically significant increase in instances of hypoglycemia. The proposed advancements provide safe control action for AP applications, personalizing and improving controller performance without the need for extensive model identification processes.

Using technology to advance type 1 diabetes care among women during the reproductive years and in pregnancy

The prevalence of diabetes is increasing globally. Technology to improve care among individuals with diabetes is constantly being developed. Women living with Type 1 Diabetes Mellitus (T1DM) have unique challenges affecting their glucose control relating to menstrual cycles, pregnancy, and menopause. The purpose of this review is to examine the literature related to the use of technology to help women with T1DM manage their diabetes during the reproductive years, pregnancy, and beyond. Continuous subcutaneous insulin infusion (CSII) therapy can provider equivalent or better glucose control when compared with multiple daily injections (MDI), with less hypoglycemia, diabetic ketoacidosis, and weight gain. The CSII therapy has features that could help improve glucose control over the menstrual cycle, menopause, and pregnancy, although the most studied of these stages is pregnancy. Continuous glucose monitoring (CGM) can be combined with any insulin delivery system (MDI or CSII) to provide data on glucose values every few minutes and show glucose trends over time. CGM introduction can highlight glucose variability for women with T1DM, may be beneficial during pregnancy, and can reduce hypoglycemia. Sensor-augmented pump therapy and hybrid artificial pancreas (closed-loop) systems are promising tools that improve outcomes among individuals with diabetes. The use of modern technology to improve glucose and metabolic control among menopausal women with diabetes has not been well studied. Internet and phone-based technologies are emerging as important tools that may help with diabetes self-care for women living with diabetes.

Near normal HbA1c with stable glucose homeostasis: the ultimate target/aim of diabetes therapy

Achieving near normal glucose homeostasis implies that all components of dysglycemia that are present in diabetes states be eliminated. Reducing ambient/overall hyperglycemia is a pre-requisite to eliminate the risk of development and progression of diabetes complications. More controversially however, are the relative and related contributions of postprandial glucose excursions, glucose variability, hypoglycemia and the dawn phenomenon across the spectrum of dysglycemia. For instance, it is likely that the dawn phenomenon contributes to ambient hyperglycemia and that postprandial glucose excursions are at the cross road of ambient hyperglycemia and glucose variability with glucose fluctuations as causative risk factors for hypoglycemia. Proof-of-concept trials such as the ongoing FLAT-SUGAR study are necessary for gaining further insight into the possible harmful effects of some of these features such as excessive glycemic variability and glucose excursions, still considered to be of minor relevance by several diabetologists. Whether their role will be more thoroughly proven through further intervention trials with "hard" endpoints, remains to be seen. In the meantime more consideration should be given to medications aimed at concomitantly reducing ambient/overall hyperglycemia and those additional abnormal glycemic features of dysglycemia.

Time dictates: emerging clinical analyses of the impact of circadian rhythms on diagnosis, prognosis and treatment of disease

Since the advent of modern molecular tools, researchers have extensively shown that essential cellular machineries have robust circadian (roughly 24 hours) variations in their pace. This molecular rhythmicity translates directly into time-of-day-dependent variation in physiology in most organ systems, which in turn provides the mechanistic rationale for why timing on a daily basis should matter in many aspects of human health. However, these basic science findings have been slow to move from bench to bedside because clinical studies are still lacking to demonstrate the importance of timing. Therefore, it has not been clear how physicians should incorporate knowledge of natural 24-hour rhythms into routine practice. This review is a brief summary of results from recently completed clinical studies on hypertension, myocardial infarction, diabetes mellitus, and adrenal dysfunction that highlights new evidence for the emerging importance of circadian rhythms in diagnosis, prognosis and treatment of disease.

Nocturnal Glucose Metabolism in Type 1 Diabetes: A Study Comparing Single Versus Dual Tracer Approaches

BACKGROUND

Understanding the effect size, variability, and underlying physiology of the dawn phenomenon is important for next-generation closed-loop control algorithms for type 1 diabetes (T1D).

SUBJECTS AND METHODS

We used an iterative protocol design to study 16 subjects with T1D on individualized insulin pump therapy for two successive nights. Endogenous glucose production (EGP) rates at 3 a.m. and 7 a.m. were measured with [6,6-(2)H(2)]glucose as a single tracer, infused from midnight to 7 a.m. in all subjects. To explore possibility of tracer recycling due to prolonged [6,6-(2)H(2)]glucose infusion, which was highly probable after preplanned interim data analyses, we infused a second tracer, [6-(3)H]glucose, from 4 a.m. to 7 a.m. in the last seven subjects to measure EGP at 7 a.m.

RESULTS

Cortisol concentrations increased during both nights, but changes in glucagon and insulin concentration were inconsistent. Although the plasma glucose concentrations rose from midnight to 7 a.m. during both nights, EGP measured with [6,6-(2)H(2)]glucose between 3 a.m. and 7 a.m. did not differ during Night 1 but fell in Night 2. However, EGP measured with [6-(3)H]glucose at 7 a.m. was higher than that measured with [6,6-(2)H(2)]glucose during both nights, thereby suggesting tracer recycling probably underestimating EGP calculated at 7 a.m. with [6,6-(2)H(2)]glucose. Likewise, EGP was higher at 7 a.m. with [6-(3)H]glucose than at 3 a.m. with [6,6-(2)H(2)]glucose during both nights.

CONCLUSIONS

The data demonstrate a consistent overnight rise in glucose concentrations through increased EGP, mediated likely by rising cortisol concentrations. The observations with the dual tracer approach imply significant tracer recycling leading to underestimation of EGP measured by longer-duration tracer infusion.

Translating What Works: A New Approach to Improve Diabetes Management

BACKGROUND

The most efficacious strategies to improve diabetes control include case management, health care team changes, patient education, and facilitated transmission of patient data to clinicians ("facilitated relay"), but these strategies have not been translated to permit general use in clinical practice.

METHODS

A web-based decision support program was developed to include these features, and assessed in patients who had A1c ≥7.0% despite using metformin with/without sulfonylureas or insulin. Staff entered patients' glucose data, obtained management recommendations, reviewed the plan with a clinician, and discussed the new plan with patients.

RESULTS

113 subjects were 96% male and 32% black, with average age 65.6 years and BMI 32.8. During prior primary care, A1c averaged 8.32 ± 0.16% (SEM). In all patients, baseline A1c was 8.18 ± 0.11%, and decreased to 7.54 ± 0.12%, 7.16 ± 0.13%, and 7.54 ± 0.16% at 3, 6, and 12 months, respectively, all P < .001. In 42 subjects who provided glucose data and made requested changes in medications, A1c was 8.12 ± 0.09% at baseline and fell to 7.29 ± 0.11%, 6.98 ± 0.10%, and 7.05 ± 0.10% at 3, 6, and 12 months, respectively, all P < .001. Chart review of 16 subjects followed for 12 months demonstrated that hypoglycemia (symptoms and/or glucose <70 mg/dl) averaged less than 1 episode/patient/month, and there was no severe hypoglycemia.

CONCLUSIONS

A novel decision support program improved A1c with little hypoglycemia. Use of this approach should allow primary care teams to keep patients well controlled, and reduce the need for specialist referrals.

Evaluation of a clinical tool to test and adjust the programmed overnight basal profiles for insulin pump therapy: a pilot study

OBJECTIVE

Clinical protocols for basal rate testing and adjustment are needed for effective insulin pump therapy. We evaluated the effects of a continuous glucose monitoring (CGM)-based semiautomated basal algorithm on glycemia.

METHODS

We developed and piloted a basal rate analyzer that interpreted CGM data from overnight fasts and recommended dose changes for subsequent nights. Subjects uploaded data online using sensor-augmented pumps for evaluation by the analyzer after each of 5 overnight fasts conducted over 2 to 8 weeks. It was designed to be conservative and iterative, making changes that did not exceed 10% at each iteration. The standard deviation and interquartile range of CGM values from midnight to 7 am (SD12-7am and IQR12-7am) over 3 baseline and 3 postintervention nights, hypoglycemia incidence (CGM values <4.0 mmol/L), and glycated hemoglobin (A1C) were compared.

RESULTS

Twenty subjects with mean ages of 38±13 years and A1C 7.6%±0.8% (60±8.7 mmol/mol) underwent the 5 iterations of basal assessments over 5±3 weeks. SD12-7am and IQR12-7am did not change from baseline to postintervention (1.57±0.8 to 1.63±0.8 mmol/L; p=0.35; 3.66±2.07 to 3.47±2.26 mmol/L; p=0.90). However, mean glucose values were lower between 2 to 3 am at baseline compared to postintervention; 3-night hypoglycemia incidence declined from 1.6±1.8 to 0.5±0.7 episodes (p=0.01), and A1C improved from 7.6%±0.8% to 7.4%±0.9% (60%±8.7% to 57%±9.8% mmol/mol; p=0.03).

CONCLUSIONS

The use of a basal rate analyzer was associated with reduced hypoglycemia and improved A1C. However, overnight glycemic stability was not improved. Further research into the efficacy of the CGM-based semiautomated algorithm is warranted.