Peripheral blood cell changes in response to acute hypoglycaemia in man

Hypoglycaemia induces a sustained pro-inflammatory response in people with type 1 diabetes and healthy controls

AIM

To determine the duration and the extension of the pro-inflammatory response to hypoglycaemia both in people with type 1 diabetes and healthy controls.

MATERIALS AND METHODS

Adults with type 1 diabetes (n = 47) and matched controls (n = 16) underwent a hyperinsulinaemic-euglycaemic hypoglycaemic (2.8 ± 0.1 mmoL/L [49.9 ± 2.3 mg/dL]) glucose clamp. During euglycaemia, hypoglycaemia, and 1, 3 and 7 days later, blood was drawn to determine immune cell phenotype, monocyte function and circulating inflammatory markers.

RESULTS

Hypoglycaemia increased lymphocyte and monocyte counts, which remained elevated for 1 week. The proportion of CD16+ monocytes increased and the proportion of CD14+ monocytes decreased. During hypoglycaemia, monocytes released more tumour necrosis factor-α and interleukin-1β, and less interleukin-10, after ex vivo stimulation. Hypoglycaemia increased the levels of 19 circulating inflammatory proteins, including high sensitive C-reactive protein, most of which remained elevated for 1 week. The epinephrine peak in response to hypoglycaemia was positively correlated with immune cell number and phenotype, but not with the proteomic response.

CONCLUSIONS

Overall, despite differences in prior exposure to hypoglycaemia, the pattern of the inflammatory responses to hypoglycaemia did not differ between people with type 1 diabetes and healthy controls. In conclusion, hypoglycaemia induces a range of pro-inflammatory responses that are sustained for at least 1 week in people with type 1 diabetes and healthy controls.

Limited impact of impaired awareness of hypoglycaemia and severe hypoglycaemia on the inflammatory profile of people with type 1 diabetes

AIM

To investigate whether a history of severe hypoglycaemia (SH) or the associated presence of impaired awareness of hypoglycaemia (IAH) is characterized by a pro-inflammatory profile in people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We measured circulating inflammatory markers and pro- and anti-inflammatory cytokine production after ex vivo stimulation of peripheral blood mononuclear cells (PBMCs) in a well-characterized cohort of individuals with type 1 diabetes (n = 239) and in people without diabetes (n = 56). Data were corrected for confounders by using multivariate linear regression models.

RESULTS

People with type 1 diabetes had higher circulating concentrations of high-sensitivity C-reactive protein (hs-CRP; 0.91 [0.36-2.25] vs. 0.52 [0.20-0.98] pg/mL, P < 0.001 and interleukin-18-binding protein (IL-18BP; 1746 [1304-2112] vs. 1381 [1191-1807] pg/mL; P = 0.001) than those without diabetes. In multivariate analysis, only higher hs-CRP concentrations persisted. Neither circulating immune cells nor ex vivo cytokine levels produced by PBMCs in response to an extensive panel of stimuli differed in groups defined by awareness state or a history of SH, apart from elevated IL-18BP in people with, versus those without, history of SH (1524 [1227-1903] vs. 1913 [1459-2408] pg/mL; P < 0.001).

CONCLUSIONS

IAH or history of SH in people with type 1 diabetes was not associated with altered inflammatory profiles, arguing against chronically elevated inflammatory activity mediating the increased cardiovascular risk associated with hypoglycaemia. The finding of higher circulating concentrations of IL-18BP in individuals with a history of SH requires further investigation.

The effect of insulin-induced hypoglycemia on inflammatory markers: A systematic review

INTRODUCTION

The effects of acute hypoglycemia on markers of inflammation have been investigated, but the results have been heterogeneous.

OBJECTIVE

We aimed to perform a systematic review about the acute effects of insulin-induced hypoglycemia on inflammatory markers in patients with diabetes as well as non-diabetic subjects.

METHODS

A systematic search of the literature using the electronic databases MEDLINE and SCOPUS was conducted through September 2017. Search terms included: "hypoglycemia"," insulin", "cytokines", and "inflammation". We included original studies assessing peripheral inflammatory markers during insulin-induced hypoglycemia in humans.

RESULTS

Two hundred twenty-two citations were initially retrieved. Eleven studies were included in our systematic review. Acute hypoglycemia increases total leukocyte number and several pro-inflammatory markers. Elevation in pro-inflammatory markers in response to insulin-induced acute hypoglycemia appears to be of similar magnitude in non-diabetic subjects and in type-1 diabetic patients with intact awareness of hypoglycemia. Adrenaline rises in response to acute hypoglycemia correlates with the increase of pro-inflammatory markers.

CONCLUSION

Acute hypoglycemia induces a pro-inflammatory state in both type-1 diabetic and non-diabetic subjects with no apparent significant difference between these two populations. Activation of the sympathetic nervous system is a likely mediator of these effects.

Exposure to hypoglycemia and risk of stroke

In the treatment of both type 1 and type 2 diabetes mellitus, maintaining a euglycemic state represents one of the key challenges. Improper dosing and administration of glucose-lowering drugs is associated with an increased risk of recurrent hypoglycemia episodes. In addition, the risk of adverse cardiovascular events in diabetic patients, particularly myocardial infarctions and strokes, is well established. Current research indicates a potential link between the baseline risk of cardio/cerebrovascular events in diabetic patients and exposure to hypoglycemia. In this review of the literature, we aim to determine if a relationship exists between recurrent hypoglycemia and adverse neurovascular events.

Asymptomatic Reactive Hypoglycemia and Inflammatory Reaction in Patients with Coronary Artery Disease

Hyperglycemia is an established risk factor of coronary artery disease (CAD). However, hyperglycemia with preserved pancreatic β cell function induces hyperinsulinemia to correct the glucose profile and may even result in reactive hypoglycemia (RH), which induces an inflammatory response. In this study, the incidence of RH and its effect on arteriosclerosis were examined in CAD patients with a lengthy oral glucose tolerance test (OGTT).We performed a prospective cross-sectional study on 116 nondiabetic CAD patients [70 ± 9 years, 70% male, HbA1c < 6.5%] using coronary angiography and a 4-hour OGTT. Blood samples were collected prior to and 4 hours after the glucose load to evaluate arteriosclerosis markers. Hypoglycemia following the glucose tolerance test was defined as blood glucose levels < 70 mg/dL. We comparatively examined markers of inflammation and arteriosclerosis between the RH group and the non-RH group.A glucose metabolism disorder was observed in 69% of the patients. Hypoglycemia was observed in 24% (28 individuals) of the patients. All showed a RH pattern with no symptoms. The RH group exhibited significantly elevated insulin levels at 1 hour. Furthermore, a significant increase in the white blood cell (WBC) count during OGTT was observed in the RH group compared with the non-RH group [delta WBC; RH: 4.84 (-4.17-20.75) versus non-RH: -2.17 (-9.23-9.09) %; P = 0.04].Asymptomatic RH and an augmentation of inflammation were observed at an incidence of 24% in CAD patients.

Admission Glucose and In-hospital Mortality after Acute Myocardial Infarction in Patients with or without Diabetes: A Cross-sectional Study

Background:

Hyperglycemia on admission has been found to elevate risk for mortality and adverse clinical events after acute myocardial infarction (AMI), but there are evidences that the relationship of blood glucose and mortality may differ between diabetic and nondiabetic patients. Prior studies in China have provided mixed results and are limited by statistical power. Here, we used data from a large, nationally representative sample of patients hospitalized with AMI in China in 2001, 2006, and 2011 to assess if admission glucose is of prognostic value in China and if this relationship differs depending on the presence or absence of diabetes.

Methods:

Using a nationally representative sample of patients with AMI in China in 2001, 2006, and 2011, we categorized patients according to their glucose levels at admission (< 3.9, 3.9–7.7, 7.8–11.0, and ≥11.1 mmol/L) and compared in-hospital mortality across these admission glucose categories, stratified by diabetes status. Among diabetic and nondiabetic patients, separately, we employed logistic regression to assess the differences in outcomes across admission glucose levels while adjusting for the same covariates.

Results:

Compared to patients with euglycemia (5.8%), patients with moderate hyperglycemia (13.1%, odds ratio [OR] = 2.44, 95% confidence interval [CI, 2.08–2.86]), severe hyperglycemia (21.5%, OR = 4.42, 95% CI [3.78–5.18]), and hypoglycemia (13.8%, OR = 2.59, 95% CI [1.68–4.00]), all had higher crude in-hospital mortality after AMI regardless of the presence of recognized diabetes mellitus. After adjustment for patients’ characteristics and clinical status, however, the relationship between admission glucose and in-hospital mortality was different for diabetic and nondiabetic patients (P for interaction = 0.045). Among diabetic patients, hypoglycemia (OR = 3.02, 95% CI [1.20–7.63]), moderate hyperglycemia (OR = 1.75, 95% CI [1.04–2.92]), and severe hyperglycemia (OR = 2.97, 95% CI [1.87–4.71]) remained associated with elevated risk for mortality, but among nondiabetic patients, only patients with moderate hyperglycemia (OR = 2.34, 95% CI [1.93–2.84]) and severe hyperglycemia (OR = 3.92, 95% CI [3.04–5.04]) were at elevated mortality risk and not hypoglycemia (OR = 1.12, 95% CI [0.60–2.08]). This relationship was consistent across different study years (P for interaction = 0.900).

Conclusions:

The relationship between admission glucose and in-hospital mortality differs for diabetic and nondiabetic patients. Hypoglycemia was a bad prognostic marker among diabetic patients alone. The study results could be used to guide risk assessment among AMI patients using admission glucose.

Trial Registration:

www.clinicaltrials.gov, NCT01624883; https://clinicaltrials.gov/ct2/show/NCT01624883

Relationship between frequency of hypoglycemic episodes and changes in carotid atherosclerosis in insulin-treated patients with type 2 diabetes mellitus

The effect of hypoglycemia on the progression of atherosclerosis in patients with type 2 diabetes mellitus (T2DM) remains largely unknown. This is a post hoc analysis of a randomized trial to investigate the relationship between hypoglycemic episodes and changes in carotid intima-media thickness (IMT). Among 274 study subjects, 104 patients experienced hypoglycemic episodes. Increases in the mean IMT and left maximum IMT of the common carotid arteries (CCA) were significantly greater in patients with hypoglycemia compared to those without hypoglycemia. Classification of the patients into three groups according to the frequency of hypoglycemic episodes showed that high frequency of hypoglycemic events was associated with increases in mean IMT-CCA, and left max-IMT-CCA and right max-IMT-CCA. In addition, repetitive episodes of hypoglycemia were associated with a reduction in the beneficial effects of sitagliptin on carotid IMT. Our data suggest that frequency of hypoglycemic episodes was associated with changes in carotid atherosclerosis.

Hypoglycemia and risk of vascular events and mortality: a systematic review and meta-analysis

AIMS

Hypoglycemia has been associated with adverse outcomes in patients with diabetes and critical illness. However, such associations in these populations have not been systematically examined.

METHODS

We conducted a systematic review and meta-analysis of longitudinal follow-up cohort studies to investigate the associations between hypoglycemia and various adverse outcomes.

RESULTS

After removing duplicates and critically appraising all screened citations, a total of 19 eligible studies were included. As demonstrated by random-effects meta-analysis, hypoglycemia was strongly associated with a higher risk of adverse events (HR 1.90, 95 % CI 1.63-2.20; P < 0.001). Comparable risk ratios were shown in prespecified stratified analyses investigating above association for different study endpoints, in patients with or without critical illness, in patients with and without diabetes (from 1.47 to 3.31; p for interaction or heterogeneity >0.1). Additionally, a dose-dependent relationship between the severity of hypoglycemia and adverse vascular events and mortality (HR for mild hypoglycemia: 1.68, 95 % CI 1.25-2.26; P < 0.001 and HR for severe hypoglycemia: 2.33, 95 % CI 2.07-2.61; P < 0.001; p for trend 0.02) was observed. Suggested by a bias analysis, the above observations were unlikely to have resulted from unmeasured confounding parameters.

CONCLUSIONS

This is the first study demonstrating that hypoglycemia was associated with comparable risk ratios in different study populations and various study endpoints, and a trend of a dose-dependent relationship between hypoglycemia severity and adverse events. The findings of this systematic review support the speculation that hypoglycemia is a risk factor for adverse vascular events and mortality.

Effect of Repetitive Glucose Spike and Hypoglycaemia on Atherosclerosis and Death Rate in Apo E-Deficient Mice

Epidemiological data suggest that postprandial hyperglycaemia and hypoglycaemia are potential risk factors for cardiovascular disease. However, the effects of repetitive postprandial glucose spikes, repetitive hypoglycaemia, and their combination on the progression of atherosclerosis remain largely unknown. The present study investigated the effects of rapid rises and falls in glucose, and their combination, on the progression of atherosclerosis in apolipoprotein (apo) E-deficient mice. In this study, apo E-deficient mice with forced oral administration of glucose twice daily for 15 weeks were used as a model of repetitive postprandial glucose spikes, and apo E-deficient mice given an intraperitoneal injection of insulin once a week for 15 weeks were used as a model of repetitive hypoglycaemia. In addition, we established a model of both repetitive postprandial glucose spikes and hypoglycaemia by combining the above interventions. Atherosclerosis was evaluated in all mice by oil red O staining. Administration of ipragliflozin, a selective inhibitor of sodium-glucose cotransporter 2, in the mouse model of repetitive glucose spikes inhibited the progression of atherosclerosis, whereas long-term repetitive glucose spikes, repetitive hypoglycaemia, and their combination had no significant impact on atherosclerosis. However, repetitive hypoglycaemia was associated with poor survival rate. The results showed that repetitive hypoglycaemia reduces the survival rate without associated progression of atherosclerosis in apo E-deficient mice.

Repetitive hypoglycemia increases circulating adrenaline level with resultant worsening of intimal thickening after vascular injury in male Goto-Kakizaki rat carotid artery

Hypoglycemia associated with diabetes management is a potential risk for cardiovascular diseases. However, the effect of hypoglycemic episodes including a surge of sympathetic activity on the progression of neointima formation after vascular injury remains largely unknown. In this study, insulin was injected intraperitoneally into nonobese diabetic Goto-Kakizaki (GK) rats, once every 3 days for 4 weeks after balloon injury of carotid artery to induce hypoglycemia. Then, we evaluated balloon injury-induced neointima formation. Insulin treatment enhanced neointima formation and increased the number of proliferating cell nuclear antigen (PCNA)-positive cells in the carotid artery. Injection of glucose with insulin prevented hypoglycemia and abrogated intimal thickening. Also, bunazosin, an α1 adrenergic receptor antagonist, prevented intimal thickening and accumulation of PCNA-positive cells induced by insulin treatment despite the presence of concomitant hypoglycemia and high adrenaline levels. Incubation of cultured smooth muscle cells with adrenaline resulted in a significant increase in their proliferation and G0/G1 to S phase progression, which was associated with activation of extracellular signal-regulated kinase, enhanced expression of cell cycle regulatory molecules such as cyclin D1, and cyclin E, and phosphorylation of retinoblastoma protein. These adrenaline-induced effects were abrogated by bunazosin. Our data indicated that increased adrenaline induced by repetitive hypoglycemia promotes intimal thickening and smooth muscle cell proliferation after endothelial denudation in GK rats.

Association of clinical symptomatic hypoglycemia with cardiovascular events and total mortality in type 2 diabetes: a nationwide population-based study

OBJECTIVE

Hypoglycemia is associated with serious health outcomes for patients treated for diabetes. However, the outcome of outpatients with type 2 diabetes who have experienced hypoglycemia episodes is largely unknown.

RESEARCH DESIGN AND METHODS

The study population, derived from the National Health Insurance Research Database released by the Taiwan National Health Research Institutes during 1998-2009, comprised 77,611 patients with newly diagnosed type 2 diabetes. We designed a prospective study consisting of randomly selected hypoglycemic type 2 diabetic patients and matched type 2 diabetic patients without hypoglycemia. We investigated the relationships of hypoglycemia with total mortality and cardiovascular events, including stroke, coronary heart disease, cardiovascular diseases, and all-cause hospitalization.

RESULTS

There were 1,844 hypoglycemic events (500 inpatients and 1,344 outpatients) among the 77,611 patients. Both mild (outpatient) and severe (inpatient) hypoglycemia cases had a higher percentage of comorbidities, including hypertension, renal diseases, cancer, stroke, and heart disease. In multivariate Cox regression models, including diabetes treatment adjustment, diabetic patients with hypoglycemia had a significantly higher risk of cardiovascular events during clinical treatment periods. After constructing a model adjusted with propensity scores, mild and severe hypoglycemia still demonstrated higher hazard ratios (HRs) for cardiovascular diseases (HR 2.09 [95% CI 1.63-2.67]), all-cause hospitalization (2.51 [2.00-3.16]), and total mortality (2.48 [1.41-4.38]).

CONCLUSIONS

Symptomatic hypoglycemia, whether clinically mild or severe, is associated with an increased risk of cardiovascular events, all-cause hospitalization, and all-cause mortality. More attention may be needed for diabetic patients with hypoglycemic episodes.

Repetitive hypoglycaemia increases serum adrenaline and induces monocyte adhesion to the endothelium in rat thoracic aorta

AIMS/HYPOTHESIS

Severe hypoglycaemia associated with diabetes management is a potential risk for cardiovascular diseases. However, the effect and mechanism of hypoglycaemia on the progression of atherosclerosis remains largely unknown. As a first step towards elucidating the above, we investigated the effect of hypoglycaemia on monocyte-endothelial interaction.

METHODS

Insulin was injected intraperitoneally once every 3 days for 5 weeks in Goto-Kakizaki rats, a non-obese rat model of type 2 diabetes. We counted the number of monocytes adherent to the endothelium of thoracic aorta as an index of early atherosclerogenesis. Cultured HUVEC were used to investigate the mechanism of action.

RESULTS

Insulin treatment increased the number of monocytes adherent to the vascular endothelium. This increase was abrogated by injection of glucose with insulin. Amosulalol, an α-1 and β-adrenoreceptor antagonist, suppressed monocyte adhesion to endothelium and levels of adhesion molecules (intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) in the endothelial surface, which had been enhanced by insulin-induced hypoglycaemia. In HUVEC, adrenaline (epinephrine) significantly increased nuclear translocation of nuclear factor-κB (NF-κB) p65 and levels of adhesion molecules, effects that were abrogated following addition of SQ22536, a specific adenyl cyclase inhibitor.

CONCLUSIONS/INTERPRETATION

Our data indicate that repetitive hypoglycaemia induced by insulin enhanced monocyte adhesion to endothelial cells in Goto-Kakizaki rat aorta through enhanced adrenaline activity and that the latter stimulated intracellular cAMP, leading to nuclear translocation of NF-κB with subsequent production of adhesion molecules in endothelial cells.

Effects of acute insulin-induced hypoglycemia on indices of inflammation: putative mechanism for aggravating vascular disease in diabetes

OBJECTIVE

To examine the effects of acute insulin-induced hypoglycemia on inflammation, endothelial dysfunction, and platelet activation in adults with and without type 1 diabetes.

RESEARCH DESIGN AND METHODS

We studied 16 nondiabetic adults and 16 subjects with type 1 diabetes during euglycemia (blood glucose 4.5 mmol/l) and hypoglycemia (blood glucose 2.5 mmol/l). Markers of inflammation, thrombosis, and endothelial dysfunction (soluble P-selectin, interleukin-6, von Willebrand factor [vWF], tissue plasminogen activator [tPA], high-sensitivity C-reactive protein [hsCRP], and soluble CD40 ligand [sCD40L]) were measured; platelet-monocyte aggregation and CD40 expression on monocytes were determined using flow cytometry.

RESULTS

In nondiabetic participants, platelet activation occurred after hypoglycemia, with increments in platelet-monocyte aggregation and P-selectin (P <or= 0.02). Inflammation was triggered with CD40 expression increasing maximally at 24 h (3.13 +/- 2.3% vs. 2.06 +/- 1.0%) after hypoglycemia (P = 0.009). Both sCD40L and hsCRP (P = 0.02) increased with a nonsignificant rise in vWF and tPA, indicating a possible endothelial effect. A reduction in sCD40L, tPA, and P-selectin occurred during euglycemia (P = 0.03, P <or= 0.006, and P = 0.006, respectively). In type 1 diabetes, both CD40 expression (5.54 +/- 4.4% vs. 3.65 +/- 1.8%; P = 0.006) and plasma sCD40L concentrations increased during hypoglycemia (peak 3.41 +/- 3.2 vs. 2.85 +/- 2.8 ng/ml; P = 0.03). Platelet-monocyte aggregation also increased significantly at 24 h after hypoglycemia (P = 0.03). A decline in vWF and P-selectin occurred during euglycemia (P <or= 0.04).

CONCLUSIONS

Acute hypoglycemia may provoke upregulation and release of vasoactive substances in adults with and without type 1 diabetes. This may be a putative mechanism for hypoglycemia-induced vascular injury.

Vascular disease and diabetes: is hypoglycaemia an aggravating factor?

Acute hypoglycaemia provokes profound physiological changes affecting the cardiovascular system and several haematological parameters, principally as a consequence of sympatho-adrenal activation and counter-regulatory hormonal secretion. Many of these responses have an important role in protecting the brain from neuroglycopenia, through altering regional blood flow and promoting metabolic changes that will restore blood glucose to normal. In healthy young adults the cardiovascular effects are transient and have no obvious detrimental consequences. However, some of the effected changes are potentially pathophysiological and in people with diabetes who have developed endothelial dysfunction, they may have an adverse impact on a vasculature that is already damaged. The acute haemodynamic and haematological changes may increase the risk of localized tissue ischaemia, and major vascular events can certainly be precipitated by acute hypoglycaemia. These include myocardial and cerebral ischaemia and occasionally infarction. Established diabetic retinopathy often deteriorates after strict glycaemic control is instituted, the latter being associated with a threefold increase in frequency of severe hypoglycaemia, and enhanced exposure to mild hypoglycaemia. The possible mechanisms underlying these hypoglycaemia-induced effects include haemorrheological changes, white cell activation, vasoconstriction, and the release of inflammatory mediators and cytokines. The concept that acute hypoglycaemia could aggravate vascular complications associated with diabetes is discussed in relation to evolving comprehension of the pathogenesis of atherosclerosis and blood vessel disease.

Plasma endothelin response to acute hypoglycaemia in adults with Type 1 diabetes

AIMS

To determine whether acute insulin-induced hypoglycaemia provokes a detectable alteration in peripheral plasma endothelin (ET) concentrations in humans with Type 1 diabetes.

METHODS

Serial plasma concentrations of ET were measured in 20 patients with Type 1 diabetes during controlled hypoglycaemia induced by intravenous infusion of soluble insulin.

RESULTS

A significant increase was observed in plasma ET concentrations, from 3.80 +/- 0.31 pg/ml at baseline to 6.72 +/- 1.47 pg/ml at 60 min after the onset of the hypoglycaemic reaction (P < 0.05).

CONCLUSIONS

Acute insulin-induced hypoglycaemia induces a rise in plasma endothelin concentrations in people with Type 1 diabetes. This finding is consistent with a putative role for ET in the mediation of hypoglycaemia-induced vasoconstriction, and the possible precipitation of macrovascular or microvascular events.

Superior mesenteric artery dilatation alone does not account for glucose-induced hypotension in human sympathetic denervation

Haemodynamic and hormonal effects of two oral isovolaemic, isoosmotic solutions of 0.5 g/kg and 1.0 g/kg glucose were studied in 10 humans with sympathetic denervation due to primary autonomic failure (AF). Measurements were made supine for 60 min, and also after 5 min 45 head-up tilt, before and 60 min after glucose. There was a similar fall in blood pressure (BP) after each dose, after 0.5 g/kg from 160+/-12 / 87+/-6 to 143+/-13 / 76+/-6 mm Hg, P < 0.05 and after 1.0 g/kg from 160+/-13 / 90+/-6 to 136+/-9 / 76+/-5 mm Hg, P < 0.05. Heart rate, cardiac index and forearm muscle blood flow did not change after either dose. After 0.5 g/kg, superior mesenteric artery blood flow was unchanged but rose significantly after 1.0 g/kg, from 243 (169-395) to 722 (227-982) ml/min, P < 0.05, 15 min after ingestion. BP fell further on tilt 60 min after each dose, but there was no difference between doses. Plasma glucose was higher after 1.0 g/kg but plasma insulin was similar after each dose. Thus, in AF with sympathetic denervation there was no dose-related effect of glucose on supine or postural hypotension. Supine hypotension after glucose was not attributable solely to increased splanchnic blood flow; other factors, including dilatation in other vascular beds may have contributed.

The influence of hypoglycaemia on regional cerebral blood flow and cerebral volume in type 1 (insulin-dependent) diabetes mellitus

The effect of moderate hypoglycaemia (venous blood glucose 2.0 +/- 0.2 mmol/l; mean +/- SD) on regional cerebral blood flow and cerebral volume was studied in a group of ten right-handed patients with Type 1 (insulin-dependent) diabetes mellitus (age 26.0 +/- 2.4 years, duration 18.4 +/- 3.8 years) using an intravenous Xenon 133 single photon emission computed tomography technique. After 10 min of hypoglycaemia, global cerebral blood flow had increased to 55.8 +/- 4.5 ml.100 g-1.min-1 compared to the initial normoglycaemic flow of 49.5 +/- 3.7 ml.100 g-1.min-1 (p < 0.01). A further increase in global cerebral blood flow to 59.5 +/- 4.5 ml.100 g-1.min-1 (p < 0.05) occurred 15 min after normalization of the blood glucose level. The global cerebral blood flow change from before hypoglycaemia to after recovery was inversely related to the initial glucose level. No change in the relative distribution of the regional cerebral blood flow was found between the measurements. The cerebral blood flow was significantly higher in the right hemisphere compared with the left hemisphere (2.3, 1.6 and 2.2%, respectively; p < 0.05) in all measurements. Deeper hypoglycemia was associated with a more pronounced decrease in brain volume, while the length of the restitution time after hypoglycaemia correlated with a volume increase. Due to influences with opposite effects there was no mean change in the brain volume.

Changes in renal function during acute insulin-induced hypoglycaemia in patients with type 1 diabetes

The effect of acute hypoglycaemia on renal function was examined in eight male patients with Type 1 diabetes who had normal urinary albumin excretion. Insulin was given as a bolus intravenous injection (0.125 U kg-1) and plasma glucose fell to a nadir of 1.6 (SE 0.2) mmol l-1, with all patients experiencing an acute autonomic reaction. Renal plasma flow fell from 674 (106) to 540 (198) ml min-1 during hypoglycaemia (p less than 0.01) and returned to 655 (181) ml min-1 (NS vs baseline). Glomerular filtration rate (GFR) declined from 143 (23) to 110 (36) ml min-1 during hypoglycaemia (p less than 0.02), rising to 150 (44) ml min-1 in the recovery period (NS vs baseline). The urinary flow rate and urinary albumin excretion rate both fell significantly in response to hypoglycaemia (10.6 (1.2) to 4.7 (1.1) ml min-1; p less than 0.002, and 46.2 (10.6) to 26.0 (10.5) micrograms min-1, respectively). Urinary dopamine excretion also declined, from 322 (37) to 211 (29) mumol min-1 (p less than 0.005) but sodium excretion was unchanged. Plasma adrenaline concentration (0.2 (0.03) to 1.7 (0.4) nmol l-1; p less than 0.01) and plasma renin activity (0.49 (0.13) to 1.08 (0.17) ng-Ang 1 l-1 h-1; p less than 0.01) increased during hypoglycaemia, but changes in plasma noradrenaline and angiotensin II levels did not attain significance. These acute changes in renal function, observed during hypoglycaemia in diabetic patients, may result from direct stimulation of the efferent sympathetic nerves to the kidney, complemented by the hormonal changes induced by hypoglycaemia.

Dual effect of insulin on plasma volume and transcapillary albumin transport

During the past decade it has been demonstrated that insulin, apart from its effects on metabolism and ion fluxes, has acute effects on the cardiovascular system and capillary permeability. Intravenous infusion of insulin in doses which increase plasma insulin to physiological levels, induced vascular dilatation and increased muscle sympathetic nerve activity during a euglycaemic glucose clamp. During similar conditions insulin increased the transcapillary escape rate of albumin and reduced plasma volume. Insulin has also an indirect effect on vascular permeability during hypoglycaemia, which is mediated by the increase in plasma adrenaline. Adrenaline infusion increased haematocrit and decreased plasma volume and intravascular albumin mass. In contrast to insulin adrenaline did not increase the transcapillary escape rate of albumin. Total autonomic blockade during insulin-induced hypoglycaemia abolished the increase in haematocrit, but did not influence the decrease in plasma volume and the increase in the transcapillary escape rate of albumin. Insulin administration may also increase urinary albumin excretion, and this effect was observed during a euglycaemic clamp. The mechanism of the increase in capillary permeability after insulin has not been elucidated. A number of morphological studies indicate that insulin may have effects on endothelial cell morphology and paraendothelial cell permeability. These results indicate that insulin, apart from its effect on peripheral blood flow, may play a role in a normal transfer of macromolecules from the blood to the extracellular space after food intake. This process may be greatly disturbed in insulin-dependent diabetic patients.

Plasma volume changes during hypoglycaemia: the effect of autonomic blockade

To investigate the role of the autonomic nervous system in changes in blood volume and composition induced by acute hypoglycaemia in man, seven healthy subjects participated in three experiments on separate days: insulin-induced hypoglycaemia with concomitant alpha-adrenoceptor blockade; insulin-induced hypoglycaemia with total autonomic blockade (alpha-adrenoceptor blockade combined with beta-adrenoceptor blockade and atropine); and insulin-induced hypoglycaemia without any autonomic blockade. In the experiments without autonomic blockade the peripheral venous hematocrit increased, plasma volume decreased, intravascular albumin content decreased and the transcapillary escape rate of albumin increased. In both experiments with autonomic blockade the increase in venous haematocrit was abolished, yet plasma volume decreased, intravascular albumin content decreased and the transcapillary escape rate of albumin increased in these experiments. Thus, the changes in plasma volume and composition in response to hypoglycaemia are due to the combined actions of adrenaline and of insulin.

Plasma volume changes during hypoglycaemia: the effect of arterial blood sampling

To investigate whether previously reported changes in venous blood volume and composition induced by acute hypoglycaemia in humans are representative for the entire body we measured erythrocyte 51Cr content, haematocrit, plasma volume, intravascular albumin content and transcapillary escape rate of albumin in arterial and venous blood in seven healthy subjects before and during insulin-induced hypoglycaemia. In both vascular sites blood 51Cr content and the haematocrit increased, plasma volume and intravascular albumin content decreased and the transcapillary escape rate of albumin increased during hypoglycaemia. The magnitude of the changes in arterial and venous blood were not significantly different. These results indicate that the above changes in blood volume and composition are whole-body phenomena: furthermore, the major part of the changes are likely to occur in tissues other than upper extremity muscles.

Duration and severity of hypoglycemia needed to induce neuropathy

The duration and severity of hypoglycemia needed to induce neuropathy is not known. To test these variables, the percentage of teased fibers of peroneal and tibial nerves showing graded pathologic abnormalities was estimated in groups of rats that had been made hypoglycemic for various times and severities one week earlier. The techniques used maintained core temperature, pO2, pCO2, and hematocrit within physiologic limits. A control group was anesthetized and mechanically ventilated but insulin was not given. A second control group underwent no experimental manipulation. Life could not be sustained with hypoglycemia below 1 mmol/l. In 23 rats that were hypoglycemic (1.4 +/- 0.2 mmol/l, mean +/- S.E.M.) for various times less than 11 h, the frequency of axonal degeneration of teased myelinated fibers (0%-1%) was not different than in controls. In 9 young rats that were hypoglycemic (1.4 +/- 0.0 mmol/l) for various times of 12 or more hours, the frequency of fiber degeneration was significantly higher than in controls (P less than 0.01) and increased to as high as 26%. By contrast, in 5 older rats that were hypoglycemic (1.5 +/- 0.1 mmol/l) for various times of 12 or more hours, the frequency of degeneration was not different from that of controls. Both duration and severity of hypoglycemia are risk factors for fiber degeneration. The peripheral nerves are more vulnerable to prolonged severe hypoglycemia in younger rats than in older rats.

Leucocyte mobilization and release of neutrophil elastase following acute insulin-induced hypoglycaemia in normal humans

Insulin-induced hypoglycaemia in humans is associated with the rapid mobilization of leucocytes in peripheral blood. The aim of the present study was to determine whether neutrophil activation, manifested in plasma by neutrophil elastase concentration, occurs in response to insulin-induced hypoglycaemia. Acute hypoglycaemia (mean blood glucose 1.3 +/- 0.2 mmol l-1; mean +/- SD) was induced with intravenous insulin in 15 normal human subjects, and provoked an increase in the neutrophil count from 3.4 (range 1.9-6.5) to 10.7 (9.4-16.3) X 10(9) l-1 (p less than 0.001), and in the total leucocyte counts from 5.7 (4.1-8.1) to 12.8 (11.3-18.6) X 10(9) l-1 (p less than 0.001), with associated elevations in plasma neutrophil elastase concentration from 21 (12-34) to 29 (14-70) micrograms l-1 (p less than 0.05), and in total neutrophil elastase concentration from 5.90 (3.13-8.20) to 25.20 (23.00-52.00) mg l-1 (p less than 0.001). As neutrophil elastase is implicated in the development of vascular disease, this rise in response to hypoglycaemia may be of pathological importance in insulin-treated diabetic patients.

The effect of alpha-adrenergic blockade on responses of peripheral blood cells to acute insulin-induced hypoglycaemia in humans

Acute hypoglycaemia provokes rapid changes in peripheral blood cell counts. To examine possible adrenergic mechanisms modulating these changes, counts of peripheral blood cells including lymphocytes, granulocytes and erythrocytes were measured in response to acute hypoglycaemia in a group of six normal subjects in control conditions (study 1), and during alpha-adrenergic blockade with phentolamine (study 2). In study 1 hypoglycaemia provoked a biphasic leucocyte response, with an early rise in lymphocyte count and a later rise in granulocyte count. The erythrocyte count increased modestly following hypoglycaemia. During alpha-adrenergic blockage, the rise in total leucocyte count was diminished, with the rise in the lymphocyte count being greatly obtunded. These findings suggest that the increments of peripheral lymphocyte and erythrocyte counts in response to acute insulin-induced hypoglycaemia are mediated via alpha-adrenoreceptors.

The effects of acute insulin-induced hypoglycaemia on renal function in normal human subjects

The effects of acute insulin-induced hypoglycaemia on renal function were studied in 8 normal male subjects. Plasma glucose (mean (SE) fell from 4.6(0.2) to 1.3(0.2) mmol l(-1), the nadir being coincident with the acute autonomic reaction, and returned to the basal value over the following 120 min. Glomerular filtration rate declined from 118(6) to 95(4) ml min-1 at the glucose nadir (p less than 0.01), and during the recovery phase returned to 118(7) ml min-1 (NS compared with basal). Renal plasma flow fell from 625(38) to 485(27) ml min-1 (p less than 0.01), rising to 545(46) ml min-1 during recovery from hypoglycaemia (NS compared with basal). Following hypoglycaemia, urinary excretion of sodium and dopamine were reduced significantly, but the albumin excretion rate was unchanged. Plasma concentrations of adrenaline, noradrenaline, angiotensin II, and plasma renin activity increased in response to hypoglycaemia. These acute changes in renal function are probably caused by sympatho-adrenal activation and secretion of catecholamines, but other hormones, such as angiotensin II, may be contributory.

Plasma volume substitution does not inhibit plasma noradrenaline and muscle nerve sympathetic responses to insulin-induced hypoglycaemia in healthy humans

Microelectrode recordings of muscle nerve sympathetic activity and measurements of venous plasma noradrenaline have indicated increased sympathetic outflow during acute hypoglycaemia. Plasma volume reduction during hypoglycaemia, as evidenced by increasing peripheral venous haematocrit might underly the sympathetic activation. To study the effect of prevention of plasma volume reduction during hypoglycaemia, saline containing albumin was infused intravenously in healthy adult volunteers during hypoglycaemia. Hypoglycaemia was induced by an intravenous injection of soluble insulin in a dose of 0.15 IU/kg body weight. Peripheral venous plasma noradrenaline concentrations were identical in experiments without and with plasma volume substitution. Muscle nerve sympathetic activity increased to the same extent during hypoglycaemia with and without plasma volume substitution. It is concluded that increased plasma noradrenaline concentrations and enhanced muscle nerve sympathetic activity during insulin-induced hypoglycaemia in man are not consequences of plasma volume reduction.

Insulin-induced hypoglycaemia and absorption of injected insulin in diabetic patients

The effect of insulin-induced hypoglycaemia (soluble insulin 1 mU kg-1 min-1 IV) on the absorption of 125I-labelled soluble insulin (10 U SC) from thigh was studied in 10 insulin-treated Type 1 diabetic patients on a test and a control day. Disappearance of 125I was followed by external gamma counting. Adipose tissue blood flow was measured concomitantly using the 133Xe-clearance technique. Arterial plasma levels of glucose, insulin, adrenaline and noradrenaline were determined intermittently. Hypoglycaemia occurred at a glucose level of 2.2 +/- 0.1 (+/- SE) mmol l-1 after 58 +/- 6 min. Peak levels of adrenaline (6.44 +/- 1.62 nmol l-1) and noradrenaline (2.29 +/- 0.39 nmol l-1) were found 10 min later. During the 30-min period after onset of hypoglycaemia, adipose tissue blood flow increased 132 +/- 45% (p less than 0.05) but the disappearance rate of 125I-insulin was unchanged. Thus, insulin absorption was unaltered in connection with hypoglycaemia in Type 1 diabetic patients, in contrast to the depression previously reported in healthy subjects, despite similar increases in adipose tissue blood flow.

Increased myocardial contractility during intravenous insulin infusion in type 1 (insulin-dependent) diabetic patients: an echocardiographic study

On two occasions eight insulin-dependent diabetic patients were connected to an artificial beta-cell, and insulin was administered by continuous intravenous infusion at a rate of 2 mU/kg/min, producing a moderate hyperinsulinaemia (mean 116 microU/ml). At random, blood glucose was kept constant by concomitant glucose infusion, or allowed to decrease to a mean value of 5.3 mmol/l. M-mode echocardiography was performed before, at 90 and at 180 min of insulin infusion. Following the euglycaemic insulin infusion periods, the fractional shortening of the left ventricle increased from 38.2% to 41.0 and 40.2%, respectively (p less than 0.02). The diastolic diameter (pre-load) and end-systolic meridional wall stress (after-load) remained constant in this experiment. In contrast, no change in fractional shortening could be demonstrated during falling blood glucose, possibly because pre-load was altered to a significant degree during this experimental condition. In conclusion, concomitant infusion of insulin and glucose, producing an euglycaemic hyperinsulinaemia, is followed by increased myocardial contractility.

Responses of peripheral blood cells and lymphocyte subpopulations to insulin-induced hypoglycaemia in human insulin-dependent (Type 1) diabetes

Changes in counts of peripheral blood cells including lymphocytes and lymphocyte subpopulations were examined in response to acute insulin-induced hypoglycaemia in fourteen insulin-dependent diabetic patients of differing duration, and in eight normal subjects. In patients with a short duration of diabetes (less than 5 years) an initial lymphocytosis preceded a later granulocytosis, similar to changes in the normal group following hypoglycaemia. The lymphocytosis comprised increments in T11 (total), T4 (helper), and T8 (suppressor/cytotoxic) lymphocyte subsets, but B lymphocytes did not rise. In diabetic patients of longer duration (greater than 15 years) the initial lymphocytosis was attenuated, the T4 subset response being absent and the T11 subset response was diminished. The lower lymphocyte responses in the long-term diabetics were unrelated to differences in the hormonal responses to hypoglycaemia or to the rate of blood glucose recovery. Rapid mobilization of specific lymphocyte subpopulations appears to be abnormal in long-term insulin-dependent diabetes, and may indicate underlying immunological dysfunction.

Plasma oxytocin, arginine vasopressin and atrial natriuretic peptide responses to insulin-induced hypoglycaemia in man

The changes in blood glucose, plasma oxytocin, plasma vasopressin, plasma atrial natriuretic peptide, serum osmolality, haematocrit and blood pressure were measured in response to acute insulin-induced hypoglycaemia in six normal male subjects. After the i.v. administration of insulin (0.15 U/kg), plasma concentrations of oxytocin and vasopressin increased rapidly in all subjects and were maximal 15 min after the acute hypoglycaemic reaction (R). Haematocrit increased at the time of the hypoglycaemic reaction, but there was no change in serum osmolality. Systolic blood pressure rose and diastolic blood pressure fell, but mean arterial blood pressure remained unchanged. No changes were demonstrated in plasma concentrations of atrial natriuretic peptide. The release of oxytocin and vasopressin in response to acute hypoglycaemia in man is probably caused by stimulation of the posterior pituitary gland via hypothalamic activation, and not by stimulation of osmoreceptors or baroreceptors.

Changes in serum apolipoprotein B concentration after oral glucose or intramuscular insulin

An oral glucose load or a single i.m. insulin injection given to normal human subjects was followed within 1 h by a fall in total serum apolipoprotein B concentration. Although both procedures caused a concomitant drop in serum albumin concentration, the apolipoprotein-B/albumin ratio fell significantly, indicating that the drop in serum apolipoprotein B concentration cannot be explained by hemodilution.

Effects of surgical stress and insulin on cardiovascular function and norepinephrine kinetics

In resting supine subjects the whole-body clearance of norepinephrine (NE) based on arterial and venous sampling averaged 1.4 and 2.5 liters/min, respectively (P less than 0.02). The difference in clearance values was due to a peripheral uptake of NE averaging 45%. The calculation of plasma NE clearance based on venous sampling results in values that are too high. The plasma appearance rate of NE increased considerably after surgery, whereas the arterial blood pressure remained unchanged. This suggests that the sensitivity to NE is reduced postsurgery. Insulin has certain acute effects on cardiovascular function and plasma NE kinetics that are unrelated to the counterregulatory response to decrements in plasma glucose concentration. Insulin may both induce antagonism to the action of NE and increase the release of NE from sympathetic nerves. Intravenous insulin decreases the plasma volume and increases the hematocrit by an adrenergic mechanism. Plasma NE increases in normal subjects after an oral glucose load. This response may be of importance because in sympathectomized patients both oral glucose and insulin administration decreases the arterial blood pressure. During an oral glucose load insulin-dependent diabetics show abnormalities in the regulation of cardiovascular function and sympathetic nervous activity that may be related to the lack of rise in endogenous insulin in these patients. These results suggest that insulin may be of importance for the normal function of the cardiovascular system.

Haemodynamic changes in insulin-induced hypoglycaemia in normal man

Haemodynamic variables (plasma volume, heart rate, blood pressure, cardiac output, stroke volume, pulmonary tissue volume, total peripheral vascular resistance, hepato-splanchnic vascular resistance, lower extremity vascular resistance and plasma catecholamines) were measured before and after insulin-induced hypoglycaemia in seven healthy men. Plasma volume decreased significantly at the nadir of glucose (mean decrease 222 +/- 41 ml) and subsequently increased to pre-hypoglycaemic values within 30 min. Cardiac output increased in response to hypoglycaemia (mean increase 2.8 +/- 0.61/min). The early rise in cardiac output was primarily due to an increase in heart rate, but later mainly due to increased stroke volume. Since pulmonary tissue volume was constant, the observed changes in cardiac output are unlikely to be due to a Frank-Starling mechanism but rather to increased sympatho-adrenal activity. Total peripheral vascular resistance as well as lower extremity vascular resistance decreased, whereas hepato-splanchnic vascular resistance was unaffected. Thus insulin-induced hypoglycaemia has marked transient effects on the circulation.