Hypoglycemia Unawareness-A Review on Pathophysiology and Clinical Implications

Hypoglycemia is a particular problem in people with diabetes while it can also occur in other clinical circumstances. Hypoglycemia unawareness describes a condition in which autonomic and neuroglycopenic symptoms of hypoglycemia decrease and hence are hardly perceivable. A failure to recognize hypoglycemia in time can lead to unconsciousness, seizure, and even death. The risk factors include intensive glycemic control, prior episodes of severe hypoglycemia, long duration of diabetes, alcohol consumption, exercise, renal failure, and sepsis. The pathophysiological mechanisms are manifold, but mainly concern altered brain glucose sensing, cerebral adaptations, and an impaired hormonal counterregulation with an attenuated release of glucagon, epinephrine, growth hormone, and other hormones, as well as impaired autonomous and neuroglycopenic symptoms. Physiologically, this counterregulatory response causes blood glucose levels to rise. The impaired hormonal counterregulatory response to recurrent hypoglycemia can lead to a vicious cycle of frequent and poorly recognized hypoglycemic episodes. There is a shift in glycemic threshold to trigger hormonal counterregulation, resulting in hypoglycemia-associated autonomic failure and leading to the clinical syndrome of hypoglycemia unawareness. This clinical syndrome represents a particularly great challenge in diabetes treatment and, thus, prevention of hypoglycemia is crucial in diabetes management. This mini-review provides an overview of hypoglycemia and the associated severe complication of impaired hypoglycemia awareness and its symptoms, pathophysiology, risk factors, consequences, as well as therapeutic strategies.

Burden and Coping Strategies of Hypoglycemia in People with Diabetes

Hypoglycemia is a limiting adverse effect of glucose-lowering medications and particularly insulin replacement therapy. This review provides insights into the burden of hypoglycemia in the management of diabetes and outlines strategies available to reduce the risk of hypoglycemia and improve patients' well-being. People with type 1 diabetes are primarily affected by hypoglycemic episodes which are associated with direct physical harms like injuries and cardiac events as well as indirect psychosocial consequences including constant anxiety, absenteeism, increased healthcare costs and overall poorer quality of life. These complications are more prominent amongst individuals with hypoglycemia unawareness or overnight hypoglycemia and could even extend to caregivers such as parents of children with diabetes. Patients experiencing frequent or severe hypoglycemic events might also develop a pathological fear of hypoglycemia and adopt aberrant behaviors intending to maintain higher blood glucose levels. Modern pharmaceutical options with a safer profile in terms of hypoglycemia are available including novel basal insulins with lower rates of nocturnal hypoglycemia along with ultra-rapid-acting insulin analogs with a shorter duration of action that might avert late post-meal hypoglycemia. Continuous glucose monitoring and sensor-augmented insulin pump therapy with low glucose suspend technology can also prevent hypoglycemia, although concerns about cost and patient satisfaction remain. Advancements in insulin therapy and technological modalities should be coupled with ongoing education and support for patients to become co-managers of their disease and reduce the risk of hypoglycemia.

Hypoglycemia unawareness among insulin-treated diabetic patients in Madinah, Saudi Arabia: prevalence and risk factors

Background

Hypoglycemia unawareness (HU) is associated with significant risks. Screening for impaired awareness of hypoglycemia in patients with diabetes is important to minimize those risks. There are limited data on the prevalence of HU in patients with diabetes in Saudi Arabia (KSA). In the current study, we investigated the frequency of HU and its risk factors among insulin treated diabetic patients in Madinah, KSA.

Methods

A cross-sectional study was conducted in a diabetes center and four primary healthcare centers at Madinha, KSA. Patients ≥14 years old with type 1 or type 2 diabetes treated with insulin for more than a year were included. HU was assessed by Clarke's and modified Pedersen-Bjergaard's scores. The risk factors for HU were determined.

Results

Of the 413 included patients, 60.3% were women, and 60.8% were on insulin alone. One-third of the participants had T1DM, while 68.5% had T2DM, with median ages of 25 and 56 years, diabetes durations of 10 and 15 years, and durations of insulin use of 10 and 5 years, respectively. The prevalence of HU was 25.2% by Clarke's survey. The risk factors for HU were poor knowledge of the patient's latest HbA1c, type of insulin, and dose of insulin. Poor medical follow-up, previous stroke, and ischemic heart disease were the other risk factors for HU. When the modified Pedersen-Bjergaard method was used, the prevalence of HU was 48.9%.

Conclusion

Despite the advances in diabetes management, HU continues to be prevalent among diabetic patients on insulin, and poor diabetes knowledge is a major risk factor. Diabetes education on self-management is of utmost importance to reduce hypoglycemia and HU.

Ghrelin does not impact the blunted counterregulatory response to recurrent hypoglycemia in mice

Introduction

Recurrent episodes of insulin-induced hypoglycemia in patients with diabetes mellitus can result in hypoglycemia-associated autonomic failure (HAAF), which is characterized by a compromised response to hypoglycemia by counterregulatory hormones (counterregulatory response; CRR) and hypoglycemia unawareness. HAAF is a leading cause of morbidity in diabetes and often hinders optimal regulation of blood glucose levels. Yet, the molecular pathways underlying HAAF remain incompletely described. We previously reported that in mice, ghrelin is permissive for the usual CRR to insulin-induced hypoglycemia. Here, we tested the hypothesis that attenuated release of ghrelin both results from HAAF and contributes to HAAF.

Methods

C57BL/6N mice, ghrelin-knockout (KO) + control mice, and GhIRKO (ghrelin cell-selective insulin receptor knockout) + control mice were randomized to one of three treatment groups: a "Euglycemia" group was injected with saline and remained euglycemic; a 1X hypoglycemia ("1X Hypo") group underwent a single episode of insulin-induced hypoglycemia; a recurrent hypoglycemia ("Recurrent Hypo") group underwent repeated episodes of insulin-induced hypoglycemia over five successive days.

Results

Recurrent hypoglycemia exaggerated the reduction in blood glucose (by ~30%) and attenuated the elevations in plasma levels of the CRR hormones glucagon (by 64.5%) and epinephrine (by 52.9%) in C57BL/6N mice compared to a single hypoglycemic episode. Yet, plasma ghrelin was equivalently reduced in "1X Hypo" and "Recurrent Hypo" C57BL/6N mice. Ghrelin-KO mice exhibited neither exaggerated hypoglycemia in response to recurrent hypoglycemia, nor any additional attenuation in CRR hormone levels compared to wild-type littermates. Also, in response to recurrent hypoglycemia, GhIRKO mice exhibited nearly identical blood glucose and plasma CRR hormone levels as littermates with intact insulin receptor expression (floxed-IR mice), despite higher plasma ghrelin in GhIRKO mice.

Conclusions

These data suggest that the usual reduction of plasma ghrelin due to insulin-induced hypoglycemia is unaltered by recurrent hypoglycemia and that ghrelin does not impact blood glucose or the blunted CRR hormone responses during recurrent hypoglycemia.

Frequency of Hypoglycemia Assessed by Continuous Glucose Monitoring in Advanced CKD

BACKGROUND

Hypoglycemia represents a risk for serious morbidity. We evaluated the prevalence and risk factors of hypoglycemia by continuous glucose monitoring (CGM) in patients with CKD with or without diabetes.

METHODS

In this cross-sectional study, outpatients with CKD stages G3-G5 (including hemodialysis) and type 2 diabetes without CKD were enrolled and underwent intermittently scanned CGM measurements for 7 days. The burden of CGM-measured hypoglycemia was assessed using the 7-day sum of area over the curve with glucose levels <70 mg/dl and the sum of time spent <54  mg/dl.

RESULTS

A total of 366 participants (148 participants with CKD and diabetes, 115 with CKD and without diabetes, and 103 without CKD and with diabetes) were included. Glucose levels of <54  mg/dl were observed in 41% of participants with CKD and diabetes, 48% of participants with CKD and without diabetes, and 14% of participants with diabetes and without CKD. However, only two participants reported hypoglycemic symptoms during CGM measurements, which were confirmed and documented by capillary blood glucose measurements. Between-group differences of 7-day area over the curve (<70 mg/dl) were as follows: hemodialysis group versus CKD stage G4 and G5 groups, -0.25 min·mg/dl per hour (95% confidence interval [CI], -6.40 to -0.59) P <0.001; CKD stage G4 and G5 groups versus CKD stage G3 group, -0.08 min·mg/dl per hour (95% CI, -0.0 to -0.50) P =0.15; and CKD stage G3 group versus diabetes without CKD group, -0.14 min·mg/dl per hour (95% CI, -0.0 to -0.20) P =0.01. In addition, the subgroup analysis of the diabetic or nondiabetic and at daytime or nighttime showed that the 7-day area over the curve (<70 mg/dl) and time spent (<54 mg/dl) was larger with worse kidney function.

CONCLUSIONS

The lowering level of kidney function was strongly associated with the burden of hypoglycemia in patients with CKD.

Pancreas Transplantation: Current Challenges, Considerations, and Controversies

Pancreas transplantation (PTx) reestablishes an autoregulating source of endogenous insulin responsive to normal feedback controls. In addition to achieving complete β-cell replacement that frees the patient with diabetes from the need to monitor serum glucose and administer exogenous insulin, successful PTx provides counterregulatory hormone secretion and exocrine function. A functioning PTx mitigates glycemic variability, eliminates the daily stigma and burden of diabetes, restores normal glucose homeostasis in patients with complicated diabetes, and improves quality of life and life expectancy. The tradeoff is that it entails a major surgical procedure and requisite long-term immunosuppression. Despite the high likelihood of rendering patients euglycemic independent of exogenous insulin, PTx is considered a treatment rather than a cure. In spite of steadily improving outcomes in each successive era coupled with expansion of recipient selection criteria to include patients with a type 2 diabetes phenotype, a decline in PTx activity has occurred in the new millennium related to a number of factors including: (1) lack of a primary referral source and general acceptance by the diabetes care community; (2) absence of consensus criteria; and (3) access, education, and resource issues within the transplant community. In the author's experience, patients who present as potential candidates for PTx have felt as though they needed to circumvent the conventional diabetes care model to gain access to transplant options. PTx should be featured more prominently in the management algorithms for patients with insulin requiring diabetes who are failing exogenous insulin therapy or experiencing progressive diabetic complications regardless of diabetes type. Furthermore, all patients with diabetes and chronic kidney disease should undergo consideration for simultaneous pancreas-kidney transplantation independent of geography or location.

Big insulin-like growth factor 2-producing multiple solitary fibrous tumors treated with debulking surgery: A case report

BACKGROUND

Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome caused by a tumor-producing high molecular weight form of insulin-like growth factor 2 (IGF2) known as big IGF2. The only curative treatment for this condition is surgical resection of the responsible tumors. However, this may not be feasible in cases with multiple metastases at diagnosis of NICTH, and no standard treatment strategy for multiple tumors has been established. The effects of pharmacological therapies including somatostatin analogs are often inefficient and remain difficult to predict.

CASE DESCRIPTION

A 68-year-old man was admitted to our hospital due to impaired consciousness and severe hypoglycemia. His medical history included diagnosis of a left temporal solitary fibrous tumor (SFT) at the age of 48 years, after which local recurrent and metastatic tumors were repeatedly resected. Four years before admission, multiple intraabdominal and subcutaneous tumors were detected and, being asymptomatic, were managed conservatively. Laboratory exam on admission demonstrated hypoglycemia accompanied with low serum insulin and IGF1 levels. Computed tomography (CT) scan revealed multiple intraabdominal and subcutaneous tumors increasing in size. Serum big IGF2 was detected on immunoblot analysis, and he was diagnosed as NICTH. In addition, tumor uptake was observed on ⁶⁸Ga-labelled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe¹-Tyr³-octreotide positron emission tomography/CT (DOTATOC-PET/CT). Since larger tumor is more suspicious about responsible producibility of big IGF2, we planned to resect large ones preferentially and reduce the amounts of residual tumors. Debulking surgery was performed by removing eleven intraabdominal tumors; the hypoglycemia was then completely corrected. Histological analyses revealed the resected tumors to be metastases of SFT having somatostatin receptor 2 expression. In immunoblot analysis, the resected tumors were found to be positive for big IGF2; serum big IGF2 was undetectable after surgery.

CONCLUSION

We present a case of NICTH with multiple metastatic SFTs. We strategically performed debulking surgery, which led to remission of hypoglycemia. This result demonstrates a pioneering practical solution for NICTH cases with multiple tumors. In addition, in cases of SFTs presenting with NICTH, positivity of DOTATOC-PET/CT as well as single-dose administration of octreotide may be predictive of the efficacy of somatostatin-based therapy.

Persistent Postgastrectomy Hypoglycemia Unawareness in Patients With Gastric Cancer Unveiled by a Prospective Study

Objective

Late dumping syndrome is a common postgastrectomy complication characterized by reactive hypoglycemia. This study aimed to explore the glycemic trend in patients who underwent gastrectomy for gastric cancer and clarify its changes over time in association with postgastrectomy symptoms.

Summary Background Data

Changes over time in glycemic trend in association with postgastrectomy symptoms have not been evaluated.

Methods

We conducted a prospective study of 71 patients who underwent curative gastrectomy for gastric cancer between November 2017 and April 2020. The patients underwent continuous glucose monitoring twice-at 1- and 12-month postgastrectomy-and were assessed using the Post-Gastrectomy Syndrome Assessment Scale 37-item questionnaire (PGSAS-37) at 1-, 6-, and 12-month postgastrectomy.

Results

Our results revealed that hypoglycemia (<70 mg/dL), especially nocturnal hypoglycemia (00:00-06:00), frequently occurred even at 12-month postgastrectomy. Hypoglycemia improved in total gastrectomy patients but remained unchanged in distal gastrectomy patients, which was still high in both groups at 12-month postgastrectomy. Glycemic variability (SD of the glycemic trend) was exacerbated in both gastrectomy groups. However, the PGSAS-37 symptom scores remained unchanged, and the living status and quality of life tended to improve. Hypoglycemia unawareness, including postprandial hypoglycemia without symptoms and nocturnal hypoglycemia, was evident even 12-month postgastrectomy.

Conclusions

Persistent postgastrectomy hypoglycemia unawareness, including late dumping syndrome without symptoms and nocturnal hypoglycemia, should be recognized as an important issue in postgastrectomy syndrome. Therefore, meticulous long-term evaluation for glycemic trends and care of patients is required.

Transplant Options for Patients With Diabetes and Advanced Kidney Disease: A Review

Optimal glycemic control in kidney transplant recipients with diabetes is associated with improved morbidity and better patient and allograft survival. Transplant options for patients with diabetes requiring insulin therapy and chronic kidney disease who are suitable candidates for kidney transplantation should include consideration of β-cell replacement therapy: pancreas or islet transplantation. International variation related to national regulatory policies exists in offering one or both options to suitable candidates and is further affected by pancreas/islet allocation policies and transplant waiting list dynamics. The selection of appropriate candidates depends on patient age, coexistent morbidities, the timing of referral to the transplant center (predialysis versus on dialysis) and availability of living kidney donors. Therefore, early referral (estimated glomerular filtration rate < 30 mL/min/1.73 m²) is of the utmost importance to ensure adequate time for informed decision making and thorough pretransplant evaluation. Obesity, cardiovascular disease, peripheral vascular disease, smoking, and frailty are some of the conditions that need to be addressed before acceptance on the transplant list, and ideally before dialysis becoming imminent. This review offers insights into selection of pancreas/islet transplant candidates by transplant centers and an update on posttransplant outcomes, which may have practice implications for referring nephrologists.

Structural Gray and White Matter Differences in Patients With Type 1 Diabetes and Impaired Awareness of Hypoglycemia

CONTEXT

Type 1 diabetes (T1D) is associated with an increased risk of cognitive decline, where severe hypoglycemia (SH) and impaired awareness of hypoglycemia (IAH) may play a role. While there is evidence of a possible association between IAH and brain damage, the potential brain changes remain poorly characterized by magnetic resonance imaging (MRI).

OBJECTIVE

To investigate whether there are structural brain differences in a group of T1D patients with IAH compared with normal awareness of hypoglycemia (NAH).

DESIGN

General practice, population-based, cross-sectional study (July 2018 to July 2019).

SETTING

Endocrinology Department, Hospital Santa Creu i Sant Pau.

PARTICIPANTS

A total of 40 T1D patients (20 each with IAH and NAH) matched for age, sex, T1D duration, and education level.

MAIN OUTCOME MEASURES

Using different neuroimaging techniques, we compared whole-brain gray matter (GM) and white matter (WM) differences. We used voxel-based morphometry and cortical surface area analysis methods to assess GM differences, and fractional anisotropy (FA) to assess WM differences.

RESULTS

Compared with patients with T1D-NAH, patients with T1D-IAH had reduced GM volumes and cortical surface areas, especially in frontal and parietal regions (P < 0.05 corrected), and also showed reduced FA values in major WM tracts. The observed MRI differences correlated with both SH frequency and IAH severity.

CONCLUSIONS

MRI for patients with T1D show that IAH is associated with brain changes involving both GM and WM. Further research is needed to elucidate whether the observed differences are a consequence of increased SH episode frequency and increased IAH severity.

Differential Expression of Inflammatory Markers in Hypoglycemia Unawareness Associated with Type 1 Diabetes: A Case Report

The recurrence of hypoglycemic episodes leads to attenuation of the normal counter-regulatory mechanisms that are controlled by the hypothalamus, which results in hypoglycemia unawareness (HU). In this case report, we described for the first time the differential expression of TNF-α, IL-1β, IL-6, and IFN-γ in a blood sample that was taken from a 27-year-old patient with type 1 diabetes mellitus (T1DM) who was diagnosed with HU. The anti-diabetic regimen is currently based on insulin injection, but the patient is planning to start the use of an insulin pump to have better control of glucose levels. Our results showed a trend toward an increase in the expression of IL-1β, IL-6, and IFN-γ in T1DM patient with HU. However, the mRNA level of TNF-α showed a significant decrease. These observations suggest that systemic inflammation could be an underlying cause of HU.

High prevalence of impaired awareness of hypoglycemia and severe hypoglycemia among people with insulin-treated type 2 diabetes: The Dutch Diabetes Pearl Cohort

OBJECTIVE

People with type 2 diabetes on insulin are at risk for hypoglycemia. Recurrent hypoglycemia can cause impaired awareness of hypoglycemia (IAH), and increase the risk for severe hypoglycemia. The aim of this study was to assess the prevalence and determinants of self-reported IAH and severe hypoglycemia in a Dutch nationwide cohort of people with insulin-treated type 2 diabetes.

RESEARCH DESIGN AND METHODS

Observational study of The Dutch Diabetes Pearl, a cohort of people with type 2 diabetes treated in primary, secondary and tertiary diabetes care centers. The presence of IAH and the occurrence of severe hypoglycemia in the past year, defined as an event requiring external help to recover, were assessed using the validated Dutch version of the Clarke questionnaire. In addition, clinical variables were collected including age, diabetes duration, hemoglobin A1c, ethnicity and education.

RESULTS

2350 people with type 2 diabetes on insulin were included: 59.1% men, mean age 61.1±10.4 years, mean diabetes duration 14.8±9.2 years and 79.5% on basal-bolus therapy. A total of 229 patients (9.7%) were classified as having IAH and 742 patients (31.6%) reported severe hypoglycemia. Increased odds for IAH were found with complex insulin regimens and lower odds with having a partner and body mass index ≥30 kg/m². Severe hypoglycemia was associated with complex insulin regimens, non-Caucasian ethnicity and use of psychoactive drugs, and inversely with metformin use.

CONCLUSIONS

In this nationwide cohort, almost one out of ten people with type 2 diabetes on insulin had IAH and >30% had a history of severe hypoglycemia in the past year.

Hypoglycemia-associated autonomic failure, counterregulatory responses, and therapeutic options in type 1 diabetes

Hypoglycemia remains a major barrier to the achievement of target levels of glycemic control for most individuals with insulin-dependent type 1 diabetes (T1D). Both the loss of β cells and an accompanying defect in the α cell response to hypoglycemia predispose patients with T1D to the development of low blood glucose. Increased glucose variability, exposure to hypoglycemia, and impaired awareness of hypoglycemia all contribute to increased risk of experiencing severe hypoglycemia, which is explained by progressive impairment in epinephrine secretion and autonomic symptom generation in response to hypoglycemia leading to defective glucose counterregulation and hypoglycemia unawareness that characterize hypoglycemia-associated autonomic failure (HAAF). Interruption of HAAF requires interfering with the mechanisms of brain adaptation to low blood glucose that affect central glucose sensing and the autonomic response to hypoglycemia, or avoidance of hypoglycemia that may allow for eventual recovery of counterregulatory and autonomic symptom responses. Strategies for hypoglycemia avoidance that include continuous glucose monitoring may reduce, but do not eliminate, clinically significant hypoglycemia, with ongoing counterregulatory defects and impaired awareness of hypoglycemia. Complete avoidance of hypoglycemia can be achieved following pancreatic islet transplantation and allows for the restoration of counterregulatory and autonomic symptom responses that evidences the potential for reversing HAAF in T1D.

Hypoglycemia Unawareness in Insulinoma Revealed with Flash Glucose Monitoring Systems

The delayed diagnosis of insulinoma remains a clinical issue. One of the main causes of such a delay is hypoglycemia unawareness. A 53-year-old woman fell unconscious during postprandial exercises. Flash glucose monitoring (FGM) systems revealed glucose profiles with fasting hypoglycemia, which facilitated the clinical diagnosis of insulinoma even though she was unaware of her hypoglycemia. The preoperative comparison of the blood glucose values provided by FGM with those obtained from capillary blood were consistent. Thus, FGM may have potential utility in revealing the presence of insulinoma-induced hypoglycemia.

Hypoglycemia: Role of Hypothalamic Glucose-Inhibited (GI) Neurons in Detection and Correction

Hypoglycemia is a profound threat to the brain since glucose is its primary fuel. As a result, glucose sensors are widely located in the central nervous system and periphery. In this perspective we will focus on the role of hypothalamic glucose-inhibited (GI) neurons in sensing and correcting hypoglycemia. In particular, we will discuss GI neurons in the ventromedial hypothalamus (VMH) which express neuronal nitric oxide synthase (nNOS) and in the perifornical hypothalamus (PFH) which express orexin. The ability of VMH nNOS-GI neurons to depolarize in low glucose closely parallels the hormonal response to hypoglycemia which stimulates gluconeogenesis. We have found that nitric oxide (NO) production in low glucose is dependent on oxidative status. In this perspective we will discuss the potential relevance of our work showing that enhancing the glutathione antioxidant system prevents hypoglycemia associated autonomic failure (HAAF) in non-diabetic rats whereas VMH overexpression of the thioredoxin antioxidant system restores hypoglycemia counterregulation in rats with type 1 diabetes.We will also address the potential role of the orexin-GI neurons in the arousal response needed for hypoglycemia awareness which leads to behavioral correction (e.g., food intake, glucose administration). The potential relationship between the hypothalamic sensors and the neurocircuitry in the hindbrain and portal mesenteric vein which is critical for hypoglycemia correction will then be discussed.

Type 1 Diabetes and Impaired Awareness of Hypoglycemia Are Associated with Reduced Brain Gray Matter Volumes

In this study, we retrospectively analyzed the anatomical MRI data acquired from 52 subjects with type 1 diabetes (26M/26F, 36 ± 11 years old, A1C = 7.2 ± 0.9%) and 50 age, sex and BMI frequency-matched non-diabetic controls (25M/25F, 36 ± 14 years old). The T1D group was further sub-divided based on whether subjects had normal, impaired, or indeterminate awareness of hypoglycemia (n = 31, 20, and 1, respectively). Our goals were to test whether the gray matter (GM) volumes of selected brain regions were associated with diabetes status as well as with the status of hypoglycemia awareness. T1D subjects were found to have slightly smaller volume of the whole cortex as compared to controls (-2.7%, p = 0.016), with the most affected brain region being the frontal lobe (-3.6%, p = 0.024). Similar differences of even larger magnitude were observed among the T1D subjects based on their hypoglycemia awareness status. Indeed, compared to the patients with normal awareness of hypoglycemia, patients with impaired awareness had smaller volume of the whole cortex (-7.9%, p = 0.0009), and in particular of the frontal lobe (-9.1%, p = 0.006), parietal lobe (-8.0%, p = 0.015) and temporal lobe (-8.2%, p = 0.009). Such differences were very similar to those observed between patients with impaired awareness and controls (-7.6%, p = 0.0002 in whole cortex, -9.1%, p = 0.0003 in frontal lobe, -7.8%, p = 0.002 in parietal lobe, and -6.4%, p = 0.019 in temporal lobe). On the other hand, patients with normal awareness did not present significant volume differences compared to controls. No group-differences were observed in the occipital lobe or in the anterior cingulate, posterior cingulate, hippocampus, and thalamus. We conclude that diabetes status is associated with a small but statistically significant reduction of the whole cortex volume, mainly in the frontal lobe. The most prominent structural effects occurred in patients with impaired awareness of hypoglycemia (IAH) as compared to those with normal awareness, perhaps due to the long-term exposure to recurrent episodes of hypoglycemia. Future studies aimed at quantifying relationships of structural outcomes with functional outcomes, with cognitive performance, as well as with parameters describing glucose variability and severity of hypoglycemia episodes, will be necessary to further understand the impact of T1D on the brain.

The Potential Cost Implications of Averting Severe Hypoglycemic Events Requiring Hospitalization in High-Risk Adults With Type 1 Diabetes Using Real-Time Continuous Glucose Monitoring

BACKGROUND

Severe hypoglycemia remains a major barrier to optimal diabetes management and places a high burden on the US health care system due to the high costs of hypoglycemia-related emergency visits and hospitalizations. Patients with type 1 diabetes (T1DM) who have hypoglycemia unawareness are at a particularly high risk for severe hypoglycemia, the incidence of which may be reduced by the use of real-time continuous glucose monitoring (RT-CGM).

METHODS

We performed a cost calculation using values of key parameters derived from various published sources to examine the potential cost implications of standalone RT-CGM as a tool for reducing rates of severe hypoglycemia requiring hospitalization in adult patients with T1DM who have hypoglycemia unawareness.

RESULTS

In a hypothetical commercial health plan with 10 million members aged 18-64 years, 9.3% (930 000) are expected to have diagnosed diabetes, with approximately 5% (46 500) having T1DM, of whom approximately 20% (9300) have hypoglycemia unawareness. RT-CGM was estimated to reduce the cost of annual hypoglycemia-related hospitalizations in this select population by $54 369 000, yielding an estimated net cost savings of $8 799 000 to $12 519 000 and a savings of $946 to $1346 per patient.

CONCLUSION

This article presents a cost calculation based on available data from multiple sources showing that RT-CGM has the potential to reduce short-term health care costs by averting severe hypoglycemic events requiring hospitalization in a select high-risk population. Prospective, randomized studies that are adequately powered and specifically enroll patients at high risk for severe hypoglycemia are needed to confirm that RT-CGM significantly reduces the incidence of these costly events.

Hypoglycemia in Type 2 Diabetes--More Common Than You Think: A Continuous Glucose Monitoring Study

BACKGROUND

Hypoglycemia is often the limiting factor for intensive glucose control in diabetes management, however its actual prevalence in type 2 diabetes (T2DM) is not well documented.

METHODOLOGY

A total of 108 patients with T2DM wore a continuous glucose monitoring system (CGMS) for 5 days. Rates and patterns of hypoglycemia and glycemic variability (GV) were calculated. Patient and medication factors were correlated with rates, timing, and severity of hypoglycemia.

RESULTS

Of the patients, 49.1% had at least 1 hypoglycemic episode (mean 1.74 episodes/patient/ 5 days of CGMS) and 75% of those patients experienced at least 1 asymptomatic hypoglycemic episode. There was no significant difference in the frequency of daytime versus nocturnal hypoglycemia. Hypoglycemia was more frequent in individuals on insulin (alone or in combination) (P = .02) and those on oral hypoglycemic agents (P < .001) compared to noninsulin secretagogues. CGMS analysis resulted in treatment modifications in 64% of the patients. T2DM patients on insulin exhibited higher glycemic variability (GV) scores (2.3 ± 0.6) as compared to those on oral medications (1.8 ± 0.7, P = .017).

CONCLUSIONS

CGMS can provide rich data that show glucose excursions in diabetes patients throughout the day. Consequently, unwarranted onset of hypo- and hyperglycemic events can be detected, intervened, and prevented by using CGMS. Hypoglycemia was frequently unrecognized by the patients in this study (75%), which increases their potential risk of significant adverse events. Incorporation of CGMS into the routine management of T2DM would increase the detection and self-awareness of hypoglycemia resulting in safer and potentially better overall control.

Hypoglycemia: The neglected complication

Hypoglycemia is an important complication of glucose-lowering therapy in patients with diabetes mellitus. Attempts made at intensive glycemic control invariably increases the risk of hypoglycemia. A six-fold increase in deaths due to diabetes has been attributed to patients experiencing severe hypoglycemia in comparison to those not experiencing severe hypoglycemia Repeated episodes of hypoglycemia can lead to impairment of the counter-regulatory system with the potential for development of hypoglycemia unawareness. The short- and long-term complications of diabetes related hypoglycemia include precipitation of acute cerebrovascular disease, myocardial infarction, neurocognitive dysfunction, retinal cell death and loss of vision in addition to health-related quality of life issues pertaining to sleep, driving, employment, recreational activities involving exercise and travel. There is an urgent need to examine the clinical spectrum and burden of hypoglycemia so that adequate control measures can be implemented against this neglected life-threatening complication. Early recognition of hypoglycemia risk factors, self-monitoring of blood glucose, selection of appropriate treatment regimens with minimal or no risk of hypoglycemia and appropriate educational programs for healthcare professionals and patients with diabetes are the major ways forward to maintain good glycemic control, minimize the risk of hypoglycemia and thereby prevent long-term complications.

Recovery of endocrine function after islet and pancreas transplantation

Long-standing type 1 diabetes (T1D) is associated with an absolute loss of endogenous insulin secretion (circulating C-peptide is undetectable) and a related defect in glucose counter-regulation that is often complicated by hypoglycemia unawareness, markedly increasing the risk for severe hypoglycemia. Both the transplantation of isolated islets and a whole pancreas can restore β-cell secretory capacity, improve glucose counter-regulation, and return hypoglycemia awareness, thus alleviating severe hypoglycemia. The transplantation of islets may require more than one donor pancreas, and the recovery of endocrine function for now appears more durable with a whole pancreas; however, islet transplantation outcomes are steadily improving. Because not all patients with T1D experiencing severe hypoglycemia are candidates to receive a whole pancreas, and since not all pancreata are technically suitable for whole organ transplantation, islet and pancreas transplantation are evolving as complementary approaches for the recovery of endocrine function in patients with the most problematic T1D.

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

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

Hypoglycemia in type 1 diabetes mellitus

Iatrogenic hypoglycemia, typically the result of the interplay of therapeutic hyperinsulinemia and compromised defenses resulting in hypoglycemia-associated autonomic failure (HAAF) in diabetes, is a problem for people with type 1 diabetes mellitus (T1DM). It causes recurrent morbidity is sometimes fatal, leads to recurrent hypoglycemia, and precludes euglycemia over a lifetime of T1DM. Risk factors include those that result in relative or absolute insulin excess and those indicative of HAAF in diabetes. Elimination of hypoglycemia from the lives of people with T1DM will likely be accomplished by new treatment methods that provide plasma glucose-regulated insulin replacement or secretion.

Glucocorticoid-deficient corticotropin-releasing hormone knockout mice maintain glucose requirements but not autonomic responses during repeated hypoglycemia

Glucocorticoids have been implicated in hypoglycemia-induced autonomic failure but also contribute to normal counterregulation. To determine the influence of normal and hypoglycemia-induced levels of glucocorticoids on counterregulatory responses to acute and repeated hypoglycemia, we compared plasma catecholamines, corticosterone, glucagon, and glucose requirements in male wild-type (WT) and glucocorticoid-deficient, corticotropin-releasing hormone knockout (CRH KO) mice. Conscious, chronically cannulated, unrestrained WT and CRH KO mice underwent a euglycemic (Prior Eu) or hypoglycemic clamp (Prior Hypo) on day 1 followed by a hypoglycemic clamp on day 2 (blood glucose both days, 65 +/- 1 mg/dl). Baseline epinephrine and glucagon were similar, and norepinephrine was elevated, in CRH KO vs. WT mice. CRH KO corticosterone was almost undetectable (<1.5 microg/dl) and unresponsive to hypoglycemia. CRH KO glucose requirements were significantly higher during day 1 hypoglycemia despite epinephrine and glucagon responses that were comparable to or greater than those in WT. Hyperinsulinemic euglycemia did not increase hormones or glucose requirements above baseline. On day 2, Prior Hypo WT had significantly higher glucose requirements and significantly lower corticosterone and glucagon responses. Prior Hypo and Prior Eu CRH KO mice had similar day 2 glucose requirements. However, Prior Hypo CRH KO mice had significantly lower day 2 epinephrine and norepinephrine vs. Prior Eu CRH KO and tended to have lower glucagon than on day 1. We conclude that glucocorticoid insufficiency in CRH KO mice correlates with 1) impaired counterregulation during acute hypoglycemia and 2) complex effects after repeated hypoglycemia, neither preventing decreased hormone responses nor worsening glucose requirements.

Effect of hypoglycemia on brain glycogen metabolism in vivo

The brain contains a small but significant amount of glycogen, which has long been considered to play an insignificant role in the brain. In this study, brain glycogen metabolism was measured using (13)C NMR spectroscopy at 9.4 T. Brain glycogen metabolism was modulated by hyperinsulinemia resulting in a net accumulation. The role of glycogen in maintaining brain function is unknown; one possibility is that it may serve as an endogenous glucose reservoir to protect the brain against severe hypoglycemia. To address this possibility, rats were subjected to insulin-induced moderate hypoglycemia and when the level of brain glucose approached zero, brain glycogen content began to decrease gradually, demonstrating utilization of this glucose reservoir. The brain glycogen signal never became undetectable, however, even during 2 hr of hypoglycemia. When plasma and brain glucose concentrations were restored, glycogen increased and the concentration exceeded the pre-hypoglycemic level by several-fold. The data suggest that brain glycogen can provide fuel for extended periods of time when glucose supply is inadequate. Furthermore, brain glycogen can rebound (super-compensate) after a single episode of hypoglycemia. We postulate that brain glycogen serves as an energy store during hypoglycemia and that it may participate in the creation of reduced physiological responses to hypoglycemia that are involved in a symptom often observed in patients with diabetes, hypoglycemia unawareness.

Acute psychotic disorder and hypoglycemia

A variable array of neuroglycopenic symptoms are frequently encountered in the hypoglycemic stage, but acute psychotic disorders are quite rare. A fifty five year old female presented with an acute psychosis following oral sulfonylurea induced hypoglycemia without preceding features of adrenomedullary stimulation. This case report suggests that an acute and transient psychotic disorder may be an important neuroglycopenic feature and its early recognition protects the patient from severe hypoglycemic brain damage in a state of hypoglycemia unawareness.