Plasma epinephrine and norepinephrine response to stimuli in autonomic neuropathy of type 2 diabetes mellitus

Pronounced cortisol response to acute psychosocial stress in type 2 diabetes patients with and without complications

It is increasingly recognized that psychological stress is linked with type 2 diabetes mellitus and its late complications. Thus, the aim of the current study was to investigate the psychophysiological response to acute psychosocial stress in patients with type 2 diabetes. In total, 53 type 2 diabetes patients with complications, 16 type 2 diabetes patients without complications, and 47 age and gender matched non-diabetic participants underwent the Trier Social Stress Test. Subjective as well as biological parameters (i.e., blood levels of cortisol, adrenocorticotropic hormone (ACTH), norepinephrine, methylglyoxal) were assessed repeatedly before and after stress induction. Data were analyzed by means of multilevel regression. Patients with type 2 diabetes showed an exaggerated cortisol response to acute stress as compared to age matched control participants (diabetes*T2 est. = 1.23, p < .001), while stress-induced alterations of ACTH and subjective parameters did not differ. Norepinephrine levels were lower among patients (diabetes est. = -4.36, p = .044) and tended to decrease earlier than in controls. The subjective reaction of type 2 diabetes patients with complications was stronger than that of patients without complications (complication*T2 est. = -1.83, p = .032), while their endocrine response to stress was similar. Stress had no effect on methylglyoxal level, and there were no group differences regarding methylglyoxal response. These results show that the cortisol reactivity of patients with type 2 diabetes to acute psychosocial stress is increased compared to a control group. Thus, alterations of the hypothalamus-pituitary-adrenal axis - especially regarding its dynamic regulation - are a plausible link between psychological stress and type 2 diabetes and its complications.

White Adipocyte Adiponectin Exocytosis Is Stimulated via β3-Adrenergic Signaling and Activation of Epac1: Catecholamine Resistance in Obesity and Type 2 Diabetes

We investigated the physiological regulation of adiponectin exocytosis in health and metabolic disease by a combination of membrane capacitance patch-clamp recordings and biochemical measurements of short-term (30-min incubations) adiponectin secretion. Epinephrine or the β₃-adrenergic receptor (AR) agonist CL 316,243 (CL) stimulated adiponectin exocytosis/secretion in cultured 3T3-L1 and in primary subcutaneous mouse adipocytes, and the stimulation was inhibited by the Epac (Exchange Protein directly Activated by cAMP) antagonist ESI-09. The β₃AR was highly expressed in cultured and primary adipocytes, whereas other ARs were detected at lower levels. 3T3-L1 and primary adipocytes expressed Epac1, whereas Epac2 was undetectable. Adiponectin secretion could not be stimulated by epinephrine or CL in adipocytes isolated from obese/type 2 diabetic mice, whereas the basal (unstimulated) adiponectin release level was elevated twofold. Gene expression of β₃AR and Epac1 was reduced in adipocytes from obese animals, and corresponded to a respective ∼35% and ∼30% reduction at the protein level. Small interfering RNA-mediated knockdown of β₃AR (∼60%) and Epac1 (∼50%) was associated with abrogated catecholamine-stimulated adiponectin secretion. We propose that adiponectin exocytosis is stimulated via adrenergic signaling pathways mainly involving β₃ARs. We further suggest that adrenergically stimulated adiponectin secretion is disturbed in obesity/type 2 diabetes as a result of the reduced expression of β₃ARs and Epac1 in a state we define as "catecholamine resistance."

Serum catecholamines and dysautonomia in diabetic gastroparesis and liver cirrhosis

BACKGROUND

Plasma catecholamine influences autonomic function and control, but there are few reports correlating them. In this study, 47 individuals (mean age, 38 years) were studied: 19 diabetes mellitus (DM) patients with gastroparesis, 16 with liver disease and 12 control subjects.

METHODS

Noninvasive autonomic function was assessed for sympathetic adrenergic functions as peripheral vasoconstriction in response to cold stress test and postural adjustment ratio (PAR) and cholinergic function as Valsalva ratio, represented by change in R-R intervals. Measurements were compared by analysis of variance and Spearman's correlation, and results were reported as mean ± standard error.

RESULTS

Plasma norepinephrine (1902.7 ± 263.3; P = 0.001) and epinephrine (224.5 ± 66.5; P = 0.008) levels, as well as plasma dopamine levels (861.3 ± 381.7), and total plasma catecholamine levels were highest for patients with liver disease, who also had significant negative correlation between norepinephrine level and vasoconstriction (P = 0.01; r = -0.5), PAR1 (P = 0.01; r = -0.5), sympathetic adrenergic functions (P = 0.005; r = -0.6), total autonomic index (P = 0.01-0.5) and total autonomic function (P = 0.01; r = -0.2) and also negative correlation between epinephrine plasma level and total autonomic function (P = 0.04; r = 0.4). DM patients were next highest in norepinephrine level (133.26 ± 7.43), but lowest for plasma catecholamine; a positive correlation between dopamine level and PAR1 (P = 0.008; r = 0.6) was also seen in this group. Plasma dopamine levels and spider score correlated negatively (P = 0.04; r = -0.5) and total plasma catecholamine positively with encephalopathy (P = 0.04; r = 0.5) in patients with liver disease.

CONCLUSIONS

Plasma catecholamine levels correlated with adrenergic functions in control subjects and patients with DM and liver disease, with no significant correlation seen for cholinergic function.

Diurnal salivary cortisol and urinary catecholamines are associated with diabetes mellitus: the Multi-Ethnic Study of Atherosclerosis

The objective was to examine the cross-sectional association of diurnal salivary cortisol curve components and urinary catecholamines with diabetes status. Up to 18 salivary cortisol samples over 3 days and overnight urinary catecholamines were collected from 1002 participants in the Multi-Ethnic Study of Atherosclerosis. Diabetes was defined as a fasting blood glucose of at least 126 mg/dL or medication use. Cortisol curve measures included awakening cortisol, cortisol awakening response, early decline, late decline, and cortisol area under the curve (AUC). Urinary catecholamines included epinephrine, norepinephrine, and dopamine. Participants with diabetes had significantly lower cortisol awakening response (β = -0.19; 95% confidence interval [CI], -0.34 to -0.04) than those without diabetes in multivariable models. Whereas men with diabetes had a nonsignificant trend toward lower total AUC (β = -1.56; 95% CI, -3.93 to 0.80), women with diabetes had significantly higher total AUC (β = 2.62; 95% CI, 0.72 to 4.51) (P = .02 for interaction) compared with those without diabetes. Men but not women with diabetes had significantly lower urinary catecholamines compared with those without diabetes (P < .05). Diabetes is associated with neuroendocrine dysregulation, which may differ by sex. Further studies are needed to determine the role of the neuroendocrine system in the pathophysiology of diabetes.

Impairment of Presynaptic ??2-Adrenoceptor-Regulated Norepinephrine Overflow in Failing Hearts from Zucker Diabetic Fatty Rats

The aim of this study was to assess whether cardiac norepinephrine overflow is affected in Type 2 diabetes mellitus. Homozygous (fa/fa) Zucker diabetic fatty (ZDF) rats were used as a model of Type 2 diabetes; heterozygous (fa/+) ZDF rats served as non-diabetic controls. Cardiac performance was determined in isolated working hearts; release of endogenous norepinephrine was induced by electrical field stimulation in Langendorff-perfused hearts. At a mean age of 30 weeks, left ventricular contraction, relaxation, and developed pressure were reduced by 20% to 35% in ZDF-fa/fa rats compared with ZDF-fa/+ rats. Stepwise increase of stimulation frequency gradually increased norepinephrine overflow in isolated hearts from both rat strains. Compared to ZDF-fa/+ rats, cardiac norepinephrine overflow was suppressed by 25% to 45% in ZDF-fa/fa rats. During presynaptic alpha2-adrenoceptor blockade with rauwolscine, increase of norepinephrine overflow was significantly higher in ZDF-fa/fa rats than in ZDF-fa/+ rats whereas alpha2-adrenoceptor activation with UK 14,304 suppressed norepinephrine overflow solely in ZDF-fa/+ rats. Myocardial tissue content of norepinephrine did not differ markedly between the two groups. In conclusion, cardiac norepinephrine overflow is inhibited in failing hearts from ZDF-fa/fa rats. This inhibition may result from a hyperactive status of presynaptic alpha2-adrenoceptors.

A new test for autonomic cardiovascular and neuroendocrine responses in diabetes mellitus: evidence for early vagal dysfunction

AIMS/HYPOTHESIS

Diabetic autonomic neuropathy affects many physiological systems, producing a variety of important clinical manifestations. It is associated with high morbidity and mortality, particularly during times of stress. This is thought to be due to an increased risk of cardiac arrhythmias, although the exact mechanisms involved have yet to be fully elucidated. The aim of the present study was to investigate the endocrine, cardiac autonomic and psychological responses of diabetic patients with and without autonomic neuropathy to a single breath of 35% CO(2).

METHODS

The 35% CO(2) challenge was performed in 20 male diabetic subjects, 11 of whom had autonomic neuropathy.

RESULTS

Baseline and stimulated cortisol, prolactin, systolic blood pressure and emotional arousal were similar in the two groups. However, subjects with autonomic neuropathy failed to demonstrate the expected CO(2)-induced bradycardia seen in the non-neuropathic patients (p<0.0001).

CONCLUSIONS/INTERPRETATION

The CO(2) challenge can be safely and easily administered to produce hypothalamic-pituitary-adrenal axis and cardiac autonomic activation, as well as emotional arousal. The test clearly distinguishes between subjects with and without cardiac autonomic neuropathy and could be an important adjunct to the methods currently available for the investigation and diagnosis of diabetic autonomic neuropathy.