Frequency of the dawn phenomenon in type 2 diabetes: implications for diabetes therapy

Assessment of postprandial hyperglycemia and circadian fluctuation of glucose concentrations in diabetic dogs using a flash glucose monitoring system

BACKGROUND

Postprandial hyperglycemia (PPH) and circadian glucose concentration fluctuations recorded in the home environment of dogs with naturally occurring diabetes mellitus (DM) have not been reported.

OBJECTIVES

To determine if a flash glucose monitoring system (FGMS; FreeStyle Libre) can detect PPH and circadian fluctuations in glucose concentrations in dogs with variably controlled DM.

ANIMALS

Fourteen client-owned dogs with DM.

METHODS

Prospective observational study. Interstitial glucose (IG) concentrations measured by the FGMS during a 13-day study period were analyzed.

RESULTS

A total of 17, 446 FGMS IG concentrations were analyzed. For all dogs analyzed together, median IG concentration measured within 30 (288 mg/dL), 60 (286 mg/dL), 90 (285 mg/dL), and 120 (285 mg/dL) minutes of meals was each significantly higher than the median IG concentration at all other times (260 mg/dL, 259 mg/dL, 258 mg/dL, and 257 mg/dL, respectively; range, 40-500 mg/dL; P < .001 for each). Median night-time IG concentration measured from all dogs on 3,547 samples recorded between 1:00 am and 6:00 am (268 mg/dL; range, 40-500 mg/dL) was significantly higher than median IG measured on 13, 899 samples at all other time points (259 mg/dL; range, 40-500 mg/dL; P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The FGMS can be used for future studies of PPH and circadian fluctuations of glucose concentrations in dogs with DM in their home environment.

Diabetes and cardiovascular disease: inter-relation of risk factors and treatment

Background

The diabetes mellitus prevalence is still advancing and increasingly becoming one of the globally most severe and expensive chronic illnesses. The strong correlation between diabetes as well as the most prominent reason for diabetes and death in diabetic patients is cardiovascular disorders. Health conditions like dyslipidemia, hypertension, obesity, and other factors of risk like the risk of cardiovascular are frequent in diabetic persons and raise the likelihood of heart attacks.

Main text

In particular, several researchers have found diabetes mellitus-related biochemical pathways that raise the likelihood of cardiovascular disorder in people with diabetes individually. This review describes diabetes-cardiovascular disorder relationships, explores potential therapeutic mechanisms, addresses existing treatment, care, and describes the directions for the future for study.

Conclusion

Thus, in individuals with diabetes, it is important to concentrate on cardiovascular threat variables to reduce the illness’s lasting cardiovascular complications. Further work to enhance knowledge of the disease state and its impact on cardiovascular function is required to boost medical treatment and cardiovascular disorders result in people with diabetes.

The importance of 24-h metabolism in obesity-related metabolic disorders: opportunities for timed interventions

Various metabolic processes in the body oscillate throughout the natural day, driven by a biological clock. Circadian rhythms are also influenced by time cues from the environment (light exposure) and behaviour (eating and exercise). Recent evidence from diurnal- and circadian-rhythm studies indicates rhythmicity in various circulating metabolites, insulin secretion and -sensitivity and energy expenditure in metabolically healthy adults. These rhythms have been shown to be disturbed in adults with obesity-related metabolic disturbances. Moreover, eating and being (in)active at a time that the body is not prepared for it, as in night-shift work, is related to poor metabolic outcomes. These findings indicate the relevance of 24-h metabolism in obesity-related metabolic alterations and have also led to novel strategies, such as timing of food intake and exercise, to reinforce the circadian rhythm and thereby improving metabolic health. This review aims to deepen the understanding of the influence of the circadian system on metabolic processes and obesity-related metabolic disturbances and to discuss novel time-based strategies that may be helpful in combating metabolic disease.

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.

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.

Metformin add-on continuous subcutaneous insulin infusion on precise insulin doses in patients with type 2 diabetes

To investigate whether metformin add-on to the continuous subcutaneous insulin infusion (Met + CSII) therapy leads to a significant reduction in insulin doses required by type 2 diabetes (T2D) patients to maintain glycemic control, and an improvement in glycemic variation (GV) compared to CSII only therapy. We analyzed data from our two randomized, controlled open-label trials. Newly diagnoses T2D patients were randomized assigned to receive either CSII therapy or Met + CSII therapy for 4 weeks. Subjects were subjected to a 4-day continuous glucose monitoring (CGM) at the endpoint. Insulin doses and GV profiles were analyzed. The primary endpoint was differences in insulin doses and GV between the two groups. A total of 188 subjects were admitted as inpatients. Subjects in metformin add-on therapy required significantly lower total, basal and bolus insulin doses than those of control group. CGM data showed that patients in Met + CSII group exhibited significant reduction in the 24-hr mean amplitude of glycemic excursions (MAGE), the standard deviation, and the coefficient of variation compared to those of control group. Our data suggest that metformin add-on to CSII therapy leads to a significant reduction in insulin doses required by T2D patients to control glycemic variations.

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.

Determining starting basal rates of insulin infusion for insulin pump users: a comparison between methods

OBJECTIVE

We aimed to assess the accuracy and safety of presently available methods of estimating starting basal insulin rates for patients with type 1 and 2 diabetes, and to compare them against an empirically derived standard basal rate and a newly developed regression formula.

RESEARCH DESIGN AND METHODS

Data on 61 patients with type 1 diabetes on continuous subcutaneous insulin infusion (CSII) therapy and 34 patients with type 2 diabetes on CSII were reviewed. Patient data were first analyzed for correlations between initial patient parameters and final basal rates. Starting basal rates were then retrospectively calculated for these patients according to the weight-based method (WB-M), the total daily dose (TDD) of insulin method (TDD-M), a flat empiric value, and a new formula developed by regression analysis of clinical data. These 4 methods were subsequently compared in their accuracy and potential risk of hypoglycemia.

RESULTS

For type 1 diabetes, patient weight and TDD of long-acting insulin correlated with final basal rates. Both the regression formula and the TDD-M appeared safer than the WB-M and empirical estimates. For type 2 diabetes, only patient TDD of long-acting insulin correlated with final basal rates. The regression formula was significantly more accurate for patients with type 2 diabetes overall, but the TDD-M estimate was marginally safer.

CONCLUSIONS

The pre-existing TDD-M was found to be the safest presently recommended estimate of initial basal rates for pump initiation in both type 1 and 2 diabetes. The best-fit regression was found to have potential use for type 2 CSII initiation.

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.

Influence of glucocorticoids and growth hormone on insulin sensitivity in humans

The seminal concept proposed by Sir Harold Himsworth more than 75 years ago that a large number of patients with diabetes were 'insulin insensitive', now termed insulin resistance, has now expanded to include several endocrine syndromes, namely those of glucocorticoid excess, and growth hormone excess and deficiency. Synthetic glucocorticoids are increasingly used to treat a wide variety of chronic diseases, whereas the beneficial effects of recombinant growth hormone replacement therapy in children and adults with growth hormone deficiency have now been well-recognized for over 25 years. However, clinical and experimental studies have established that increased circulating levels of glucocorticoids and growth hormone can also lead to worsening of insulin resistance, glucose intolerance, overt diabetes mellitus and cardiovascular disease. Improved understanding of the physiological 24-h rhythmicity of glucocorticoid and growth hormone secretion and its influence on the dawn phenomenon and the Staub-Trauggot effect has therefore led to renewed interest in studies on the mechanisms of insulin resistance induced by exogenous administration of glucocorticoids and growth hormone in humans. In this review, we describe the physiological events that result from the presence of resistance to insulin action at the level of skeletal muscle, adipose tissue, and liver, describe the known mechanisms of glucocorticoid- and growth hormone-mediated insulin resistance, and provide an update of the contributions of glucocorticoids and growth hormone to understanding the pathophysiology of insulin resistance and its effects on several endocrine syndromes.

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

OBJECTIVE

To know whether age has an independent effect on the dawn phenomenon in noninsulin-using type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eighty-one individuals with type 2 diabetes were matched for HbA(1c) and divided by age into three subgroups of 27 individuals (1: ≥70 years; 2: 60-69 years; and 3: ≤59 years). All underwent ambulatory continuous glucose monitoring for quantifying the dawn phenomenon (i.e., the absolute [∂G, mg/dL] or relative [∂G%] increments from nocturnal nadirs to prebreakfast time points).

RESULTS

HbA(1c) levels and 24-h glycemic profiles were similar across the three groups. Glucose increments (mean ± SEM) were identical in the three groups: ∂G (mg/dL), 22.0 ± 4.7 (1), 21.3 ± 3.6 (2), and 18.0 ± 3.6 (3) and δG (%), 19.9 ± 4.9 (1), 21.6 ± 4.4 (2), and 17.6 ± 4.2 (3). Using the most common definition (∂G >10 mg/dL), the prevalence of the dawn phenomenon was 52, 70, and 59% in groups 1, 2, and 3, respectively.

CONCLUSIONS

The dawn phenomenon is present in the elderly.

Analysis of factors influencing nitrogen balance during acute starvation in obese subject with and without type 2 diabetes

BACKGROUND & AIMS

Patients with type 2 diabetes (T2DM) tend to loose more lean body mass during both long-term weight reduction and short-term very-low-calorie diet. We ask what factors influence protein loss during acute starvation in T2DM.

METHODS

In a prospective in-hospital observational study, we compared 10 subjects with T2DM and 10 age-weight-sex matched obese controls (OB) during 60 h of fasting and used frequent blood sampling and indirect calorimetry to describe metabolic and endocrine response. We analyzed factors influencing nitrogen balance using stepwise multiple regressions.

RESULTS

Despite comparable pattern of plasma insulin, free fatty acid, 3-hydroxybutyrate and almost identical behavior of growth hormone axis, our T2DM subjects remained hyperglycaemic and in contrast to OB subjects they failed to reduce the rate of protein oxidation, even though muscle protein breakdown rate declined similarly in both groups. Regression analysis revealed that protein oxidation rate in T2DM group was enhanced by hyperglycemia and sympathetic activity and suppressed by circulating insulin and 3-hydroxybutyrate. Liver insulin resistance increases peripheral insulin concentrations and enhances the conversion of non-esterified fatty acids (NEFA) to ketones and thus it might be a protein-saving factor.

CONCLUSION

Relative deficiency of circulating insulin and hyperglycemia play a pivotal role in the impairment of protein sparing in T2DM during a short-term fasting.

The Dawn Phenomenon Revisited: Implications for Diabetes Therapy

OBJECTIVE

To summarize current data on the magnitude, prevalence, variability, pathogenesis, and management of the dawn phenomenon in patients with diabetes mellitus.

METHODS

On the basis of the pertinent available literature and clinical experience, we propose a quantitative definition of the dawn phenomenon, discuss potential pathogenic mechanisms, and suggest management options.

RESULTS

The "dawn phenomenon" is a term used to describe hyperglycemia or an increase in the amount of insulin needed to maintain normoglycemia, occurring in the absence of antecedent hypoglycemia or waning insulin levels, during the early morning hours. To be clinically relevant, the magnitude of the dawn increase in blood glucose level should be more than 10 mg/dL or the increase in insulin requirement should be at least 20% from the overnight nadir. Controversy exists regarding the frequency, reproducibility, and pathogenesis of the dawn phenomenon. Approximately 54% of patients with type 1 diabetes and 55% of patients with type 2 diabetes experience the dawn phenomenon when the foregoing quantitative definition is used. The most likely pathogenic mechanism underlying the dawn phenomenon is growth hormone-mediated impairment of insulin sensitivity at the liver and muscles. The exact biochemical pathways involved are unknown. Therapeutic decisions aimed at correcting fasting hyperglycemia should take into account the variability and magnitude of the dawn phenomenon within individual patients. Successful insulinization appears to minimize the effects of the dawn phenomenon. Currently, no subcutaneous depot preparation of insulin exists that is capable of mimicking the basal insulinsecretion of the healthy pancreas.

CONCLUSION

Increases in the bedtime doses of hypoglycemic agents with nighttime peaks in action may correct early morning hyperglycemia but be associated with undesirable nocturnal hypoglycemia. Targeted continuous subcutaneous insulin infusion programming can facilitate the prevention of early morning hyperglycemia in selected patients.