Reversal of hypoglycemia unawareness in a long-term type 1 diabetic patient by improvement of beta-adrenergic sensitivity after prevention of hypoglycemia

Hypoglycemic unawareness: challenges, triggers, and recommendations in patients with hypoglycemic unawareness: a case report

Background

Hypoglycemia is a fairly common complication in diabetic patients, particularly in those on insulin therapy. Hypoglycemia symptoms are classified into two types: autonomic and neuroglycopenic symptoms. If a person develops neuroglycopenic symptoms before the appearance of autonomic symptoms or is asymptomatic until blood sugar levels are very low, the patient will develop hypoglycemic unawareness (HU).

Case presentation

A 25-year-old Iranian woman with HU presented with a severe hypoglycemic episode. This episode was characterized by loss of consciousness and focal neural deficits, which were unusual symptoms in the patient, who was a medical intern with type 1 diabetes and currently being treated with regular and NPH insulin.

Conclusions

Hypoglycemia is a common complication in diabetic patients receiving oral or insulin therapy. A patient who is unaware of their condition may experience severe and potentially fatal episodes. These incidents can negatively affect their daily lives as well as their careers and jobs. Hypoglycemia-associated autonomic failure is a possible cause for patients with multiple episodes of severe hypoglycemia. IThe use of a continuous glucose monitoring device with an alarm, if available, can be an excellent option for these patients.

Carvedilol prevents impairment of the counterregulatory response in recurrently hypoglycaemic diabetic rats

Aim

It has been suggested that repeated activation of the adrenergic system during antecedent episodes of hypoglycaemia contributes to the development of counterregulatory failure. We previously reported that treatment with carvedilol, a non-specific β-blocker, prevented the development of counterregulatory failure and improved hypoglycaemia awareness in recurrently hypoglycaemic non-diabetic rats. The current study investigated whether carvedilol has similar benefits in diabetic rats.

Methods

Recurrently hypoglycaemic streptozotocin-diabetic rats (STZ+RH) were treated with carvedilol for one week prior to undergoing a hypoglycaemic clamp. Hypoglycaemia awareness was evaluated in streptozotocin-diabetic rats made hypoglycaemia unaware using repeated injections of 2-deoxyglucose.

Results

Compared to hypoglycaemia-naïve STZ-diabetic controls, exogenous glucose requirements were more than doubled in the STZ+RH animals and this was associated with a 49% reduction in the epinephrine response to hypoglycaemia. Treating STZ+RH animals with carvedilol improved the epinephrine response to hypoglycaemia. Of note, neither recurrent hypoglycaemia nor carvedilol treatment affected the glucagon response in diabetic animals. Additionally, carvedilol treatment improved the feeding response to insulin-induced hypoglycaemia in diabetic animals made 'hypoglycaemia unaware' using repeated injections of 2-deoxyglucose, suggesting the treatment improved awareness of hypoglycaemia as well.

Conclusion

Our data suggest that carvedilol may be useful in preventing impairments of the sympathoadrenal response and the development of hypoglycaemia unawareness during recurring episodes of hypoglycaemia in diabetic animals.

Repetitive hypoglycemia reduces activation of glucose-responsive neurons in C1 and C3 medullary brain regions to subsequent hypoglycemia

The impaired ability of the autonomic nervous system to respond to hypoglycemia is termed "hypoglycemia-associated autonomic failure" (HAAF). This life-threatening phenomenon results from at least two recent episodes of hypoglycemia, but the pathology underpinning HAAF remains largely unknown. Although naloxone appears to improve hypoglycemia counterregulation under controlled conditions, hypoglycemia prevention remains the current mainstay therapy for HAAF. Epinephrine-synthesizing neurons in the rostroventrolateral (C1) and dorsomedial (C3) medulla project to the subset of sympathetic preganglionic neurons that regulate peripheral epinephrine release. Here we determined whether or not C1 and C3 neuronal activation is impaired in HAAF and whether or not 1 wk of hypoglycemia prevention or treatment with naloxone could restore C1 and C3 neuronal activation and improve HAAF. Twenty male Sprague-Dawley rats (250-300 g) were used. Plasma epinephrine levels were significantly increased after a single episode of hypoglycemia (n = 4; 5,438 ± 783 pg/ml vs. control 193 ± 27 pg/ml, P < 0.05). Repeated hypoglycemia significantly reduced the plasma epinephrine response to subsequent hypoglycemia (n = 4; 2,179 ± 220 pg/ml vs. 5,438 ± 783 pg/ml, P < 0.05). Activation of medullary C1 (n = 4; 50 ± 5% vs. control 3 ± 1%, P < 0.05) and C3 (n = 4; 45 ± 5% vs. control 4 ± 1%, P < 0.05) neurons was significantly increased after a single episode of hypoglycemia. Activation of C1 (n = 4; 12 ± 3%, P < 0.05) and C3 (n = 4; 19 ± 5%, P < 0.05) neurons was significantly reduced in the HAAF groups. Hypoglycemia prevention or treatment with naloxone did not restore the plasma epinephrine response or C1 and C3 neuronal activation. Thus repeated hypoglycemia reduced the activation of C1 and C3 neurons mediating adrenal medullary responses to subsequent bouts of hypoglycemia.

Interdisciplinary approach to compensation of hypoglycemia in diabetic patients with chronic heart failure

Diabetes mellitus is a chronic disease requiring lifelong control with hypoglycemic agents that must demonstrate excellent efficacy and safety profiles. In patients taking glucose-lowering drugs, hypoglycemia is a common cause of death associated with arrhythmias, increased thrombus formation, and specific effects of catecholamines due to sympathoadrenal activation. Focus is now shifting from merely glycemic control to multifactorial approach. In the context of individual drugs and classes, this article reviews interdisciplinary strategies evaluating metabolic effects of drugs for treatment of chronic heart failure (CHF) which can mask characteristic hypoglycemia symptoms. Hypoglycemia unawareness and cardiac autonomic neuropathy are discussed. Data suggesting that hypoglycemia modulates immune response are reviewed. The potential role of gut microbiota in improving health of patients with diabetes and CHF is emphasized. Reports stating that nondiabetic CHF patients can have life-threatening hypoglycemia associated with imbalance of thyroid hormones are discussed. Regular glycemic control based on HbA1c measurements and adequate pharmacotherapy remain the priorities in diabetes management. New antihyperglycemic drugs with safer profiles should be preferred in vulnerable CHF patients. Multidrug interactions must be considered. Emerging therapies with reduced hypoglycemia risk, telemedicine, sensor technologies, and genetic testing predicting hypoglycemia risk may help solving the challenges of hypoglycemia in CHF patients with diabetes. Interdisciplinary work may involve cardiologists, diabetologists/endocrinologists, immunologists, gastroenterologists, microbiologists, nutritionists, imaging specialists, geneticists, telemedicine experts, and other relevant specialists. This review emphasizes that systematic knowledge on pathophysiology of hypoglycemia in diabetic patients with CHF is largely lacking and the gaps in our understanding require further discoveries.

Mechanisms of hypoglycemia unawareness and implications in diabetic patients

Hypoglycemia unawareness (HU) is defined at the onset of neuroglycopenia before the appearance of autonomic warning symptoms. It is a major limitation to achieving tight diabetes and reduced quality of life. HU occurs in approximately 40% of people with type 1 diabetes mellitus (T1DM) and with less frequency in T2DM. Though the aetiology of HU is multifactorial, possible mechanisms include chronic exposure to low blood glucose, antecedent hypoglycaemia, recurrent severe hypoglycaemia and the failure of counter-regulatory hormones. Clinically it manifests as the inability to recognise impeding hypoglycaemia by symptoms, but the mechanisms and mediators remain largely unknown. Prevention and management of HU is complex, and can only be achieved by a multifactorial intervention of clinical care and structured patient education by the diabetes team. Less know regarding the impact of medications on the development or recognition of this condition in patients with diabetes. Several medications are thought to worsen or promote HU, whereas others may have an attenuating effect on the problem. This article reviews recent advances in how the brain senses and responds to hypoglycaemia, novel mechanisms by which people with insulin-treated diabetes develop HU and impaired counter-regulatory responses. The consequences that HU has on the person with diabetes and their family are also described. Finally, it examines the evidence for prevention and treatment of HU, and summarizes the effects of medications that may influence it.

Hypoglycemia and safe driving

The lack of awareness of the effects of hypoglycemia on safe driving is a real issue for diabetic patients and a challenge for health care providers. Taking the form of questions and answers, this review addresses the issue of road traffic accidents and drivers with type 1 diabetes mellitus. While there is little evidence showing higher accident rates among diabetic drivers, there is research indicating that hypoglycemia compromises driving performance, resulting in slower response times and reduced cognitive function. Unawareness of an early fall in plasma glucose is another important issue that affects some diabetic drivers. The driver with type 1 diabetes is obliged to check their blood glucose before driving. The physician's duty is to familiarize the patient with the risk of hypoglycemia. If hypoglycemic unawareness is present, the physician should advise the patient to stop driving until the condition is reversed. The doctor should consider informing authorities if he concludes there is a risk and the driver cannot be persuaded to stop driving.

Effects of glycemic control on target organ responses to epinephrine in type 1 diabetes

Severe hypoglycemia occurs in intensively treated patients with type 1 diabetes mellitus (T1DM) due in part to deficient epinephrine counterregulatory responses. Previously, we have found that T1DM patients demonstrated a spectrum of altered responses to epinephrine at a variety of target organs compared with nondiabetic healthy subjects. What is not known is whether intensive glycemic control further modifies target organ responses in individuals with T1DM. Therefore, the aim of this study is to assess whether there is tissue specific (liver, muscle, adipose tissue, pancreas and cardiovascular) resistance to epinephrine in intensively controlled (IC) T1DM compared with those with conventional control (CC). Eight IC patients (age 33 +/- 4 yr, BMI 24 +/- 2 kg/m2, Hb A1C 6.7 +/- 0.1%), and 11 CC patients (age 35 +/- 3 yr, BMI 25 +/- 1 kg/m2, Hb A1C 9.6 +/- 0.1%) underwent two separate randomized, single-blind, 2-h hyperinsulinemic euglycemic clamp studies with (EPI) and without (NO EPI) epinephrine infusion. Epinephrine levels during EPI were similar in all groups (5,197 +/- 344 pmol/l). Glucose (5.3 +/- 0.1 mmol/l) and insulin levels (515 +/- 44 pmol/l) were similar in all groups during the glucose clamps. Endogenous glucose production (EGP) and glucose uptake (R(d)) were determined using [3-H3]glucose. Muscle biopsy was performed at the end of each study. IC had a significantly reduced EGP and R(d) responses to EPI compared with CC. Glucagon responses to EPI were similarly blunted in both IC and CC. Free fatty acid and glycerol response to EPI was greater in CC compared with IC. There was a significantly greater systolic blood pressure response to EPI in CC. We conclude that, despite similar epinephrine, insulin, and glucose levels, intensively treated T1DM patients had reduced cardiovascular, skeletal muscle, hepatic, and adipose target organ responses to EPI compared with conventionally treated T1DM patients.