Frequency and severity of the dawn phenomenon in type 2 diabetes: relationship to age

A probabilistic computation framework to estimate the dawn phenomenon in type 2 diabetes using continuous glucose monitoring

In type 2 diabetes (T2D), the dawn phenomenon is an overnight glucose rise recognized to contribute to overall glycemia and is a potential target for therapeutic intervention. Existing CGM-based approaches do not account for sensor error, which can mask the true extent of the dawn phenomenon. To address this challenge, we developed a probabilistic framework that incorporates sensor error to assign a probability to the occurrence of dawn phenomenon. In contrast, the current approaches label glucose fluctuations as dawn phenomena as a binary yes/no. We compared the proposed probabilistic model with a standard binary model on CGM data from 173 participants (71% female, 87% Hispanic/Latino, 54 ± 12 years, with either a diagnosis of T2D for six months or with an elevated risk of T2D) stratified by HbA1c levels into normal but at risk for T2D, with pre-T2D, or with non-insulin-treated T2D. The probabilistic model revealed a higher dawn phenomenon frequency in T2D [49% (95% CI 37-63%)] compared to pre-T2D [36% (95% CI 31-48%), p = 0.01] and at-risk participants [34% (95% CI 27-39%), p < 0.0001]. While these trends were also found using the binary approach, the probabilistic model identified significantly greater dawn phenomenon frequency than the traditional binary model across all three HbA1c sub-groups (p < 0.0001), indicating its potential to detect the dawn phenomenon earlier across diabetes risk categories.

Dual-basal-insulin regimen for the management of dawn phenomenon in children with type 1 diabetes: a retrospective cohort study

Background

Handling of the dawn phenomenon (DP) with multiple daily insulin injection (MDII) regimen is a real challenge.

Objective

We aimed to demonstrate the effectiveness of a dual-basal-insulin (a long-acting glargine and an intermediate-acting neutral protamine Hagedorn (NPH)) regimen for the management of DP in children with type 1 diabetes mellitus (T1DM). The primary efficacy outcome was to overcome morning hyperglycemia without causing hypoglycemia during the non-DP period of the night.

Design

Retrospective cohort study.

Method

Charts of 28 children with T1DM (12 female; 42.8%, mean age 13.7 ± 2.1 years) treated with MDII were retrospectively reviewed. The median duration of diabetes was 4.5 years (range 2-13.5 years). DP was diagnosed using a threshold difference of 20 mg/dL (0.1 mmol/L) between fasting capillary blood glucose at 3 a.m. and prebreakfast. NPH was administered at midnight in addition to daily bedtime (08.00-09.00 p.m.) glargine (dual-basal-insulin regimen). Midnight, 03:00 a.m., prebreakfast and postprandial capillary blood glucose readings, insulin-carbohydrate ratios, and basal-bolus insulin doses were recorded the day before the dual-basal-insulin regimen was started and the day after the titration of the insulin doses was complete. Body mass index standard deviation scores (BMI SDS) at the onset-3rd-12th month of treatment were noted.

Results

Before using dual basal insulin, prebreakfast capillary blood glucose levels were greater than those at midnight and at 03:00 a.m. (F = 64.985, p < 0.01). After titration of the dual-basal-insulin doses, there were significant improvements such that there were no statistically significant differences in the capillary blood glucose measurements at the three crucial time points (midnight, 03.00 a.m., and prebreakfast; F = 1.827, p = 0.172). No instances of hypoglycemia were reported, and the total daily insulin per kilogram of body weight did not change. The BMI SDS remained steady over the course of the 1-year follow-up.

Conclusion

In this retrospective cohort study, the dual-basal-insulin regimen, using a long-acting glargine and an intermediate-acting NPH, was effective in overcoming early morning hyperglycemia due to insulin resistance in the DP. However, the effectiveness of the dual-basal-insulin regimen needs to be verified by prospective controlled studies using continuous glucose monitoring metrics or frequent blood glucose monitoring.

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.

Adipocyte Subpopulations Mediate Growth Hormone-induced Lipolysis and Glucose Tolerance in Male Mice

In adipose tissue, growth hormone (GH) stimulates lipolysis, leading to an increase in plasma free fatty acid levels and a reduction in insulin sensitivity. In our previous studies, we have found that GH increases lipolysis by reducing peroxisome proliferator-activated receptor γ (PPARγ) transcription activity, leading to a reduction of tat-specific protein 27 (FSP27, also known as CIDEC) expression. In previous studies, our laboratory uncovered 3 developmentally distinct subpopulations of white adipocytes. In this manuscript, we show that one of the subpopulations, termed type 2 adipocytes, has increased GH-induced signaling and lipolysis compared to other adipocyte subtypes. To assess the physiological role of GH-mediated lipolysis mediated by this adipocyte subpopulation, we specifically expressed human FSP27 (hFSP27) transgene in type 2 adipocytes (type2Ad-hFSP27tg mice). Systemically, male type2Ad-hFSP27tg mice displayed reduced serum glycerol release and nonesterified fatty acids levels after acute GH treatment, and improvement in acute, but not chronic, GH-induced glucose intolerance. Furthermore, we demonstrate that type2Ad-hFSP27tg mice displayed improved hepatic insulin signaling. Taken together, these results indicate that this adipocyte subpopulation is a critical regulator of the GH-mediated lipolytic and metabolic response. Thus, further investigation of adipocyte subpopulations may provide novel treatment strategies to regulate GH-induced glucose intolerance in patients with growth and metabolic disorders.

Exploring the Impact of Dawn Phenomenon on Glucose-Guided Eating Thresholds in Individuals With Type 2 Diabetes Using Continuous Glucose Monitoring: Observational Study

BACKGROUND

Glucose-guided eating (GGE) improves metabolic markers of chronic disease risk, including insulin resistance, in adults without diabetes. GGE is a timed eating paradigm that relies on experiencing feelings of hunger and having a preprandial glucose level below a personalized threshold computed from 2 consecutive morning fasting glucose levels. The dawn phenomenon (DP), which results in elevated morning preprandial glucose levels, could cause typically derived GGE thresholds to be unacceptable or ineffective among people with type 2 diabetes (T2DM).

OBJECTIVE

The aim of this study is to quantify the incidence and day-to-day variability in the magnitude of DP and examine its effect on morning preprandial glucose levels as a preliminary test of the feasibility of GGE in adults with T2DM.

METHODS

Study participants wore a single-blinded Dexcom G6 Pro continuous glucose monitoring (CGM) system for up to 10 days. First and last eating times and any overnight eating were reported using daily surveys over the study duration. DP was expressed as a dichotomous variable at the day level (DP day vs non-DP day) and as a continuous variable reflecting the percent of days DP was experienced on a valid day. A valid day was defined as having no reported overnight eating (between midnight and 6 AM). ∂ Glucose was computed as the difference in nocturnal glucose nadir (between midnight and 6 AM) to morning preprandial glucose levels. ∂ Glucose ≥20 mg/dL constituted a DP day. Using multilevel modeling, we examined the between- and within-person effects of DP on morning preprandial glucose and the effect of evening eating times on DP.

RESULTS

In total, 21 adults (59% female; 13/21, 62%) with non-insulin-treated T2DM wore a CGM for an average of 10.5 (SD 1.1) days. Twenty out of 21 participants (95%) experienced DP for at least 1 day, with an average of 51% of days (SD 27.2; range 0%-100%). The mean ∂ glucose was 23.7 (SD 13.2) mg/dL. People who experience DP more frequently had a morning preprandial glucose level that was 54.1 (95% CI 17.0-83.9; P<.001) mg/dL higher than those who experienced DP less frequently. For within-person effect, morning preprandial glucose levels were 12.1 (95% CI 6.3-17.8; P=.008) mg/dL higher on a DP day than on a non-DP day. The association between ∂ glucose and preprandial glucose levels was 0.50 (95% CI 0.37-0.60; P<.001). There was no effect of the last eating time on DP.

CONCLUSIONS

DP was experienced by most study participants regardless of last eating times. The magnitude of the within-person effect of DP on morning preprandial glucose levels was meaningful in the context of GGE. Alternative approaches for determining acceptable and effective GGE thresholds for people with T2DM should be explored and evaluated.

Relationship Between Time in Range and Dusk Phenomenon in Outpatients with Type 2 Diabetes Mellitus

Purpose

The dusk phenomenon refers to a spontaneous and transient pre-dinner hyperglycemia that affects glucose fluctuation and glycemic control, and the increasing use of continuous glucose monitoring (CGM) has facilitated its diagnosis. We investigated the frequency of the dusk phenomenon and its relationship with the time in range (TIR) in patients with type 2 diabetes mellitus (T2DM).

Patients and Methods

This study involved 102 patients with T2DM who underwent CGM for 14 days. CGM-derived metrics and clinical characteristics were evaluated. A consecutive dusk blood glucose difference (pre-dinner glucose minus 2-hour post-lunch glucose) of ≥ 0 or once-only dusk blood glucose difference of < 0 was diagnosed as the clinical dusk phenomenon (CLDP).

Results

We found that the percentage of CLDP was 11.76% (10.34% in men, 13.64% in women). Compared with the non-CLDP group, the CLDP group tended to be younger and have a lower percentage of TIR (%TIR^3.9-10) and higher percentage of time above range (%TAR^>10 and %TAR^>13.9) (P ≤ 0.05). Adjusted for confounding factors, the binary logistic regression analysis showed a negative association of CLDP with %TIR (odds ratio < 1, P < 0.05). We repeated the correlation analysis based on 70%TIR and found significant differences in hemoglobin A1c, fasting blood glucose, mean blood glucose, standard deviation of the sensor glucose values, glucose coefficient of variation, largest amplitude of glycemic excursions, mean amplitude of glycemic excursions, glucose management indicator, and percentage of CLDP between the two subgroups of TIR ≤ 70% and TIR > 70% (P < 0.05). The negative association between TIR and CLDP still remained after adjustment by the binary logistic regression analysis.

Conclusion

The CLDP was frequently present in patients with T2DM. The TIR was significantly correlated with the CLDP and could serve as an independent negative predictor.

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.

Correlation Between Mean Amplitude of Glycemic Excursion and Bone Turnover Markers in Patients with Type 2 Diabetes: A Cross-Sectional Study

OBJECTIVE

The present study explores the relationship between glycemic excursion and bone turnover markers.

METHODS

A total of 250 patients with type 2 diabetes mellitus (T2DM) (142 female and 108 male patients) were enrolled in this study. All participants underwent 72 hours of continuous glycemic monitoring to evaluate the mean amplitude of glycemic excursions (MAGE) of each person. Bone turnover markers and other biochemical data were measured for each patient. Linear regression was performed to explore the relationship between bone turnover markers and glycemic excursion. A value of P < 0.05 was considered statistically significant.

RESULTS

MAGE was negatively correlated to N-terminal propeptide of type 1 collagen (P1NP) female: [odds ratios (95% confidence interval) (OR (95% CI)), -2.516 (-5.389, 0.356)]; male: [-2.895, (-6.521, -0.731)] and C-terminal telopeptide fragments of type-I collagen (β-CTX) female [-0.025, (-0.036, 0.005)]; male [-0.043, (-0.082, 0.003)]. MAGE was still negatively correlated with β-CTX female [-0.036, (-0.198, -0.030)]; male [-0.048, (-0.089, -0.007)] after adjusting for clinical data and biochemical indices.

CONCLUSION

An independent negative relationship between glycemic excursion and bone turnover markers in patients with T2DM was identified in this study.

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.

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.

Association of sleep quality with glycemic variability assessed by flash glucose monitoring in patients with type 2 diabetes

BACKGROUND

Deterioration of sleep quality has been reported to contribute to the incidence of diabetes and may be responsible for glycemic status in diabetes. The present study explored the relationship between sleep quality and glycemic variability in patients with type 2 diabetes (T2D).

METHODS

We recruited 111 patients with T2D for this cross-sectional study. Each patient underwent flash glucose monitoring for 14 days to obtain glycemic variability parameters, such as standard deviation of glucose (SD), coefficient of variation of glucose (CV), mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), and time in glucose range of 3.9-10 mmol/L (TIR_3.9-10). After 14 days of flash glucose monitoring, each patient received a questionnaire on the Pittsburgh Sleep Quality Index (PSQI) to evaluate subjective sleep quality. HbA1c was also collected to assess average glucose.

RESULTS

HbA1c was comparable among the subgroups of PSQI score tertiles. Across ascending tertiles of PSQI scores, SD, CV and MAGE were increased, while TIR_3.9-10 was decreased (p for trend  <  0.05), but not MODD (p for trend  =  0.090). Moreover, PSQI scores were positively correlated with SD, CV, MODD and MAGE (r =  0.322, 0.361, 0.308 and 0.354, respectively, p  <  0.001) and were inversely correlated with TIR_3.9-10 (r  =  - 0.386, p  <  0.001). After adjusting for other relevant data by multivariate linear regression analyses, PSQI scores were independently responsible for SD (β  =  0.251, t  =  2.112, p  =  0.041), CV (β  =  0.286, t  =  2.207, p  =  0.033), MAGE (β  =  0.323, t  =  2.489, p  =  0.018), and TIR_3.9-10 (β  =  - 0.401, t  =  - 3.930, p  <  0.001) but not for MODD (β  =  0.188, t  =  1.374, p  =  0.177).

CONCLUSIONS

Increased glycemic variability assessed by flash glucose monitoring was closely associated with poor subjective sleep quality evaluated by the PSQI in patients with T2D.

The impact of dusk phenomenon on total glucose exposure in Chinese people with type 2 diabetes

This study was aimed at assessing the impact of the dusk phenomenon on the total glucose exposure in Chinese people with type 2 diabetes.A total of 380 type 2 diabetes who received a retrospective continuous glucose monitoring system (CGMs) for 72 hours were enrolled in our study, 32 of them failed in CGMs. The patients were first divided into 2 groups: dusk phenomenon (n = 95) and non dusk phenomenon group (n = 253). The magnitude of the dusk phenomenon (δDusk) was quantified by pre-dinner glucose minus post-lunch 2 hours glucose. A persistent δDusk ≥ 0 or a once only δDusk < 0 can be diagnosed with the dusk phenomenon. The participants were secondarily matched for the post-lunch 2 hours glucose to assess the impact of the dusk phenomenon on the overall glucose exposure. The impact of the dusk phenomenon was assessed on high-performance liquid chromatography assay (HbA1c) and 24-hour mean glucose.There were 95 of 348 (27.3%) participants with the dusk phenomenon in the overall population, and the median of δDusk level was -0.8 (-1.8, 0.2) mmol/L. The median of glucose differences between the 2 paired groups were 0.4 (-0.4, 1.0)% for HbA1c, 0.9 (0.2, 1.4) mmol/L for 24 hours mean glucose. The correlation analysis showed no relationship between the magnitude of dawn phenomenon and the dusk phenomenon (r = 0.052, P = .472).The incidence of dusk phenomenon is about 27.3% in people with type 2 diabetes. The impacts of dusk phenomenon on HbA1c and 24-hour mean glucose were about 0.4% and 0.9 mmol/L and the dusk phenomenon was not related with the dawn phenomenon.

Effect of growth hormone on insulin signaling

Growth hormone (GH) is a pleiotropic hormone that coordinates an array of physiological processes, including effects on bone, muscle, and fat, ultimately resulting in growth. Metabolically, GH promotes anabolic action in most tissues except adipose, where its catabolic action causes the breakdown of stored triglycerides into free fatty acids (FFA). GH antagonizes insulin action via various molecular pathways. Chronic GH secretion suppresses the anti-lipolytic action of insulin and increases FFA flux into the systemic circulation; thus, promoting lipotoxicity, which causes pathophysiological problems, including insulin resistance. In this review, we will provide an update on GH-stimulated adipose lipolysis and its consequences on insulin signaling in liver, skeletal muscle, and adipose tissue. Furthermore, we will discuss the mechanisms that contribute to the diabetogenic action of GH.

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.

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.

Impact of free-living pattern of sedentary behaviour on intra-day glucose regulation in type 2 diabetes

Purpose

To investigate how the pattern of sedentary behaviour affects intra-day glucose regulation in type 2 diabetes.

Methods

This intensive longitudinal study was conducted in 37 participants with type 2 diabetes (age, 62.8 ± 10.5 years). Glucose and sedentary behaviour/physical activity were assessed with a continuous glucose monitoring (Abbott FreeStyle Libre) and an activity monitor (activPAL3) for 14 days. Multiple regression models with generalised estimating equations (GEEs) approach were used to assess the associations of sedentary time and breaks in sedentary time with pre-breakfast glucose, pre-lunch glucose, pre-dinner glucose, post-breakfast glucose, post-lunch glucose, post-dinner glucose, bedtime glucose, the dawn phenomenon, time in target glucose range (TIR, glucose 3.9–10 mmol/L) and time above target glucose range (TAR, glucose > 10 mmol/L).

Results

Sedentary time was associated with higher pre-breakfast glucose (p = 0.001), pre-dinner glucose (p < 0.001), post-lunch glucose (p = 0.005), post-dinner glucose (p = 0.013) and the dawn phenomenon (p < 0.001). Breaks in sedentary time were associated with lower pre-breakfast glucose (p = 0.023), pre-dinner glucose (p = 0.023), post-breakfast glucose (p < 0.001) and the dawn phenomenon (p = 0.004). The association between sedentary time and less TIR (p = 0.022) and the association between breaks in sedentary time and more TIR (p = 0.001) were also observed.

Conclusions

Reducing sedentary time and promoting breaks in sedentary time could be clinically relevant to improve intra-day glucose regulation in type 2 diabetes.

Electronic supplementary material

The online version of this article (10.1007/s00421-019-04261-z) contains supplementary material, which is available to authorized users.

The fluctuation in sympathetic nerve activity around wake-up time was positively associated with not only morning but also daily glycemic variability in subjects with type 2 diabetes

AIMS

It is known that autonomic nerve activity (ANA) affects glucose metabolism by regulating the secretion of insulin and glucagon. Sympathetic nerve stimulation results in increased blood glucose levels. ANA also showed a circadian variation, and sympathetic nerve activity was minimal at night and began to rise at arousal. Therefore, a drastic alteration in ANA around wake-up would be associated with glycemic variability (GV) known risk factor for cardiovascular disease. We investigated the relation between ANA around wake-up and either morning or daily GV.

METHODS

We simultaneously performed Holter ECG and continuous glucose monitoring system in 41 patients with type 2 diabetes (T2D). ANA was assessed by heart rate variability (HRV) analysis. Delta (Δ) wake-up was defined as the difference between the maximum and minimum value during 1 h before and after wake-up time, before breakfast.

RESULTS

Δ of low frequency/high frequency (LF/HF) around wake-up time (Δ LF/HF _wake-up) was positively associated with Δ glucose _wake-up, standard deviation (SD) glucose _wake-up, the mean amplitude of glucose excursions (MAGE_24h), and SD glucose_24h after adjustment for age, sex, BMI, the duration of diabetes, and the prevalence of diabetic polyneuropathy (β = 0.47, p = 0.011, β = 0.48, p = 0.009, β = 0.54, p = 0.002 and β = 0.41, p = 0.0025, respectively). No association was found between Δ LF/HF_wake-up and either mean blood glucose for 24 h, or HbA1c as parameters of chronic hyperglycemia.

CONCLUSIONS

In T2D, the fluctuation in fasting sympathetic nerve activity around wake-up was positively associated with not only morning but also daily GV.

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.

Growth hormone controls lipolysis by regulation of FSP27 expression

Growth hormone (GH) has long been known to stimulate lipolysis and insulin resistance; however, the molecular mechanisms underlying these effects are unknown. In the present study, we demonstrate that GH acutely induces lipolysis in cultured adipocytes. This effect is secondary to the reduced expression of a negative regulator of lipolysis, fat-specific protein 27 (FSP27; aka Cidec) at both the mRNA and protein levels. These effects are mimicked in vivo as transgenic overexpression of GH leads to a reduction of FSP27 expression. Mechanistically, we show GH modulation of FSP27 expression is mediated through activation of both MEK/ERK- and STAT5-dependent intracellular signaling. These two molecular pathways interact to differentially manipulate peroxisome proliferator-activated receptor gamma activity (PPARγ) on the FSP27 promoter. Furthermore, overexpression of FSP27 is sufficient to fully suppress GH-induced lipolysis and insulin resistance in cultured adipocytes. Taken together, these data decipher a molecular mechanism by which GH acutely regulates lipolysis and insulin resistance in adipocytes.

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.

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.

Comparison of morning basal + 1 bolus insulin therapy (insulin glulisine + insulin glargine 300 U/mL vs insulin lispro + insulin glargine biosimilar) using continuous glucose monitoring: A randomized crossover study

INTRODUCTION

We compared the effects of morning administration of insulin glulisine + insulin glargine 300 U/mL (G + G300) with that of insulin lispro + insulin glargine biosimilar (L + GB).

MATERIALS AND METHODS

A total of 30 patients with type 2 diabetes who wore a continuous glucose monitoring device on admission after glucose levels were stabilized by morning long-acting and ultra-rapid-acting insulins were randomly allocated to groups who received G + G300 on days 1 and 2, and the same dose L + GB on days 3 and 4, or vice versa. Data collected on days 2 and 4 (mean amplitude of glycemic excursion, mean of daily differences: all days) were analyzed. Insulin was injected at 08.00 h. A day was defined as the period from 08.00 h one day, to 08.00 h the next day. Test meals were given.

RESULTS

Increased post-breakfast glucose level, post-breakfast glucose gradient, mean glucose level, standard deviation and M-value (24 h, 00.00-06.00 h), mean amplitude of glycemic excursion, and mean of daily differences were significantly lower in patients taking G + G300 than those taking L + GB (P ≤ 0.0001-0.04). The area over the glucose curve (<70 mg/dL) was not significantly different between groups. Pre-lunch - pre-breakfast glucose levels were significantly lower in patients taking L + GB than those taking G + G300 (P < 0.0001). The difference in the highest post-breakfast glucose level between groups (Δ = G + G300 - L + GB) was significantly correlated to 24-h mean glucose level (r = 0.40, P = 0.03).

CONCLUSIONS

Compared with L + GB, G + G300 decreases post-breakfast glucose level reducing rate of rise of that, nocturnal and 24-h glucose variability and level without causing hypoglycemia, and daily variance.

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.

Investigating the Relationship between Morning Glycemic Variability and Patient Characteristics Using Continuous Glucose Monitoring Data in Patients with Type 2 Diabetes

Objective To investigate the relationship between patient characteristics and morning glycemic variability. Methods We retrospectively evaluated 106 patients with type 2 diabetes who underwent continuous glucose monitoring during admission. The highest postprandial glucose level (within 3 hours after breakfast; 'highest level'), the time from the start of breakfast to the highest postprandial glucose level ('highest time'), the difference between the pre-breakfast and highest postprandial breakfast glucose level ('increase'), the area under the curve (AUC; ≥180 mg/dL) for the glycemic variability within 3 hours after breakfast ('morning AUC'), and the post-breakfast glucose gradient ('gradient') were calculated. We analyzed the associations between these factors and nocturnal hypoglycemia and the patients' characteristics by using a regression analysis. Results After stepwise multivariate adjustment, significant independent associations were found between 'highest level' and high age, low BMI, and high HbA1c; 'highest time' and high HbA1c, low C-peptide immunoreactivity (CPR), and low fasting plasma glucose (FPG); the 'increase' and high age, low BMI, high HbA1c, low FPG and hypoglycemia; 'morning AUC' and high age, high HbA1c and hypoglycemia; and 'gradient' and long duration of diabetes and low BMI. Conclusion Higher age and lower BMI are associated with higher 'highest' and 'increase' levels. Higher HbA1c levels were linked to a longer 'highest time', and longer durations of the diabetes, while lower BMI values were related to a higher 'gradient'.

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.

Major Increases between Pre- and Post-breakfast Glucose Levels May Predict Nocturnal Hypoglycemia in Type 2 Diabetes

Objective The aim of this study was to determine whether nocturnal hypoglycemia may be predicted according to morning glucose levels. Methods We retrospectively evaluated 106 patients with type 2 diabetes who underwent continuous glucose monitoring during admission. The pre-breakfast glucose level (Pre-breakfast level), highest postprandial glucose level within 3 hours after breakfast (Highest level), time from the start of breakfast to the highest postprandial glucose level (Highest time), difference between the pre-breakfast and highest postprandial breakfast glucose levels (Increase), area under the glucose curve (≥180 mg/dL) within 3 hours after breakfast (Morning AUC), post-breakfast glucose gradient (Gradient), and the increase-to-pre-breakfast ratio (Increase/Pre-breakfast) were calculated. The subjects were divided into hypoglycemic and non-hypoglycemic patients and compared for the above parameters using the t-test. A receiver operating characteristic analysis was used to determine the optimal cut-off values to predict nocturnal hypoglycemia (Hypoglycemia). Results Twenty-eight patients (26.4%) had hypoglycemia. The Pre-breakfast levels were significantly lower in patients with hypoglycemia than those without (p=0.03). The Increases were significantly higher in patients with hypoglycemia than those without (p=0.047). The Increase/Pre-breakfast ratio were significantly larger in patients with hypoglycemia than those without (p=0.0002). Their cut-off values were as follows (level, sensitivity, specificity, and area under the curve): 123 mg/dL, 0.89, 0.55, and 0.78 (p<0.0001); 90.5 mg/dL, 0.75, 0.64, and 0.76 (p<0.0001); and 90.2%, 0.75, 0.76, and 0.78 (p<0.0001), respectively. Conclusion Major increases between the pre- and post-breakfast glucose levels may predict nocturnal hypoglycemia in patients with type 2 diabetes.

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.

The Effectiveness and Risks of Programming an Insulin Pump to Counteract the Dawn Phenomenon in Type 1 Diabetes

OBJECTIVE

Continuous subcutaneous insulin infusion (CSII) programming for an early morning increase in insulin delivery is frequently recommended to counteract the rise in glucose prior to breakfast (dawn phenomenon). However, both the effectiveness and safety of this approach have not been tested in the ambulatory setting. Using continuous glucose monitoring, we investigated the safety and effectiveness of early morning CSII programming for management of the dawn phenomenon in subjects with type 1 diabetes.

METHODS

We conducted a controlled, observational eight-month longitudinal study of type 1 diabetic patients (n=40). Reproducibility of the dawn phenomenon was determined in subjects treated with multiple daily injections of insulin (MDI, n=12) and those on CSII who did not program an early morning increase in insulin delivery (CSII non-programmers, n=8). The effects of early morning CSII programming were determined by comparing rates of the dawn phenomenon and hypoglycemia in CSII non-programmers versus CSII-users who programmed an early morning increase in insulin delivery (CSII programmers, n=20).

RESULTS

The dawn phenomenon occurred in all tested subjects to a variable extent (median rate 56% of nights). CSII programming was not associated with a reduction in the occurrence of the dawn phenomenon (42%) compared to non-programmers (48%) (P=0.47) nor in the magnitude of the dawn phenomenon. Hypoglycemia occurred more frequently in the CSII programmers (37%) compared to non-programmers (18%) (P=0.001).

CONCLUSION

The dawn phenomenon occurs unpredictably; therefore, early morning CSII programming for a fixed increase in early morning insulin delivery is ineffective and may be hazardous to the patient.

Magnitude of the dawn phenomenon and its impact on the overall glucose exposure in type 2 diabetes: is this of concern?

OBJECTIVE

To assess the magnitude of the dawn phenomenon and its impact on the total glucose exposure in type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 248 noninsulin-treated persons with type 2 diabetes who underwent continuous glucose monitoring were divided into three groups selected by treatments: diet alone (n = 53); insulin sensitizers alone (n = 82); and insulin secretagogues alone or in combination with insulin sensitizers (n = 113). The dawn phenomenon (∂ glucose, mg/dL) was quantified by its absolute increment from nocturnal nadir to prebreakfast value. The participants were secondarily divided into two paired subsets after they had been separated by the presence/absence of a dawn phenomenon based on a threshold of 20 mg/dL and matched for glucose nadir. The impact of the dawn phenomenon was assessed on HbA1c and 24-h mean glucose.

RESULTS

The median of ∂ glucose (interquartile range) was 16.0 (0-31.5 mg/dL) in the 248 subjects, and no differences were observed across groups selected by HbA1c or treatments. In the overall population, the mean impacts on HbA1c and 24-h mean glucose were 4.3 ± 1.3 mmol/mol (0.39 ± 0.12%) and 12.4 ± 2.4 mg/dL, respectively. The mean impact on 24-h mean glucose was not statistically different between those on diet alone (16.7 ± 5.9 mg/dL) compared with the two subsets treated with oral hypoglycemic agents (11.2 ± 5.3 and 8.5 ± 7.5 mg/dL).

CONCLUSIONS

The impact of the dawn phenomenon on overall glycemic control in type 2 diabetes, as depicted by the HbA1c level, was ∼0.4% and not eliminated by any of the currently available armamentarium of oral antidiabetes agents.