Adrenomedullary hyperactivity in type I diabetic patients before and during continuous subcutaneous insulin treatment

Altered neuroendocrine sleep architecture in patients with type 1 diabetes

OBJECTIVE

The modulatory influence of nocturnal sleep on neuroendocrine secretory activity is increasingly recognized as a factor critical to health. Disturbances of sleep may arise from and contribute to the disease process in chronically ill patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Using standard polysomnography and repetitive blood sampling, neuroendocrine sleep architecture was assessed under well-controlled nonhypoglycemic conditions in 14 type 1 diabetic patients and 14 healthy control subjects matched for age, sex, and BMI.

RESULTS

As expected, plasma glucose (P = 0.02) and serum insulin (P < 0.001) levels were constantly higher in type 1 diabetic patients than in healthy subjects throughout the night. Beside these characteristic alterations of glucose metabolism, type 1 diabetic patients displayed higher blood levels of growth hormone (P = 0.001) and epinephrine (P = 0.02) during the entire night and higher levels of ACTH (P = 0.01) as well as a tendency toward higher cortisol levels (P = 0.072) during the first night-half, compared with healthy control subjects. Patients spent slightly less time in slow wave sleep (P = 0.09) during the first night-half (where this sleep stage predominates), and overall exhibited an increased proportion of stage 2 sleep (P = 0.01). Correspondingly, assessment of mood and symptoms after sleep revealed that subjective sleep was less restorative in type 1 diabetic patients than in healthy subjects.

CONCLUSIONS

Our data indicate distinct alterations in the neuroendocrine sleep architecture of patients with type 1 diabetes, which add to the generally adverse impact of the disease on the patients' health.

Changes in blood pressure and plasma catecholamine levels during prolonged hyperinsulinemia

Hyperinsulinemia has been shown to induce activation of the sympathetic nervous system and vasodilatation. Whether these effects result in changes in blood pressure (BP) is discussed controversially. We measured BP and plasma catecholamine levels in 30 healthy men during a 60-minute baseline phase and 360-minute period of insulin infusion. In a double-blind, between-subject comparison, insulin was infused at a low rate (1.5 mU insulin/kg per minute) in one half of the subjects and at a high rate (15 mU/kg per minute) in the other half. Throughout the experiments, blood glucose levels were held constantly within the normal range by a simultaneous infusion of glucose. Serum insulin levels increased to a plateau of 543 +/- 34 pmol/L during low rate and to 24,029 +/- 1,595 pmol/L during high rate of insulin infusion. Compared with baseline, insulin infusion of either rate significantly increased systolic BP, BP amplitude, and heart rate (all P < .05). In comparison with the low rate of insulin infusion, the high rate provoked a more pronounced increase in heart rate (P < .02) and systolic BP (P < .05) but tended to decrease diastolic BP (P < .08) summing up to a distinctly more increased BP amplitude (P < .05). Plasma norepinephrine as well as epinephrine levels did not significantly change during the low-rate insulin infusion but significantly increased during high-rate insulin infusion (both P < .05). By showing a dose-dependent increasing influence of insulin on systolic BP and circulating catecholamine levels, the present study provides experimental evidence for the notion that hyperinsulinemia contributes to the development of hypertension.

Alpha-2 adrenergic activity in perimenopausal women

Lipid alterations and increased blood pressure may occur during perimenopause. No data are available in perimenopausal women on the alpha-2 adrenergic activity which affects norepinephrine secretion. We studied cardiovascular and catecholamine responses to clonidine (300 mg per os) in a group of 15 perimenopausal women (PeriMW) and in a control group of 13 premenopausal women (PreMW). Nine of the perimenopausal women were also studied after 4-month percutaneous estrogen replacement therapy (PeriMWE). Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), plasma norepinephrine (NE) and epinephrine (E) were evaluated before and at 120 min, 130 min, 140 min after clonidine administration. Basal values of SBP, DBP and HR were not different (F = 0.7, p = NS; F = 0.2, p = NS and F = 0.1, p = NS respectively) between PeriMW both before and after therapy and PreMW. Resting levels of E were similar in PreMW and in PeriMW before and during estrogen therapy (F = 0.8, p = NS); PeriMW showed higher basal NE levels both before and during estrogen therapy than PreMW (F = 12; p < 0.001). Clonidine administration decreased SBP, DBP and NE levels in PreMW, in PeriMW and in PeriMWE without any difference between the groups (F = 1.2, p = NS; F = 0.5, p = NS and F = 1.3, P = NS respectively). HR decreased significantly after clonidine in PreMW (F = 5.4, p < 0.03) but not in PeriMW before (F = 1.0, p = NS) and during estrogen therapy (F = 0.5, p = NS). Clonidine did not affect plasma E in the three groups studied (F = 2.8, p = NS; F = 2.2, P = NS and F = 0.1, p = NS). The present study demonstrates that increased basal plasma NE levels are present in PeriMW. The cardiovascular and catecholamine response to clonidine in PeriMW both before and during estrogen therapy are similar to those observed in PreMW, suggesting a normal inhibitory alpha-2 receptor pathway.

Stress and the erectile response to intracavernosal prostaglandin E1 in men with erectile dysfunction

The erectile response to intracavernosal injection (ICI) of smooth muscle relaxants is often impaired in men with presumed psychogenic erectile dysfunction. This study tests the hypothesis that such impairment results from stress-related increase in circulating norepinephrine (NE). Fifty-nine men with erectile dysfunction had their nocturnal penile tumescence (NPT) monitored over 2 nights, and ICI of 10 micrograms prostaglandin E1 was given on the second morning. Psychometric and neuroendocrine measures of stress, including plasma and urinary catecholamines, were taken on both mornings. Inhibition of the ICI response was determined by the difference between NPT and ICI responses, and two groups of "high inhibition" and "low inhibition" men were compared. The high inhibition group showed higher "Trait" and "State" anxiety and a neuroendocrine profile of higher initial cortisol and lower plasma catecholamine levels than the low inhibition group. These differences were evident on both mornings and hence were not specifically related to the ICI. There was no support for the hypothesis that inhibition of response to ICI results from increased circulating NE, though the possibility that increased NE release occurred specifically in the erectile tissues could not be excluded.

Voluntary exercise improves glycemia in non-obese diabetic (NOD) mice

The non-obese diabetic (NOD) mouse was used to investigate the effects of voluntary wheel running exercise on blood glucose levels, glycosylated hemoglobin, and longevity in Type 1 diabetes mellitus. In Experiment 1, diabetic and normoglycemic mice exercised 5 h/day, 5 days/week for 3 weeks matched with non-exercising controls. In diabetic animals a positive correlation was found between blood glucose and the number of revolutions performed (P < or = 0.02). Exercise also significantly lowered blood glucose between baseline and post-exercise in both diabetic and normoglycemic animals. In Experiment 2, mice exercised 2 h/day, 5 days/week. For the diabetic animals, glycosylated hemoglobin was lower than that of matched non-exercising diabetic animals at week 3 (11.1 +/- 0.6% vs. 15.0 +/- 1.6%, P < 0.001). Diabetic runners were able to train and significantly increased running in the first 4 weeks (P < 0.05). At the end of 9 weeks all 5 diabetic runners were alive, compared with 3 of 5 non-running diabetic animals. We conclude: (i) the NOD mouse is a useful model for the study of exercise in Type 1 diabetes, (ii) running exercise is associated with a drop in blood glucose, (iii) the amount of voluntary exercise performed correlates with blood glucose in diabetic animals, and (iv) diabetic mice will increase running distance in the first few weeks after diagnosis.

Daily variations in catecholamine excretion are not influenced by very low calorie diet in obese women

The increase in metabolic efficiency during energy restriction seems to be an established phenomenon in obese patients. The sympathoadrenal system is involved in the control of energy expenditure and the catecholamine responses to stimuli vary during the day. We therefore studied the circadian pattern of urinary catecholamine excretion during 4-h collections for two consecutive days in a group of 20 obese female patients during and after a very low calorie diet (500 kcal/die). The diet period induced a significant weight loss in all the patients studied (99.1 +/- 3.7 vs 92.5 +/- 4.1 Kg; p < 0.01). The mean daily excretion of epinephrine did not change after 24 days of diet restriction when compared with the value obtained at the 4th day (12.0 +/- 2.5 vs 10.3 +/- 2.2 nmol/4 h respectively; p = NS) while a slight decrease was observed in the mean daily excretion of norepinephrine (52.5 +/- 8.7 vs 66.6 +/- 9.3 nmol/4 h respectively; p = NS). A circadian rhythm was detected for epinephrine and norepinephrine excretion both during and after very low calorie diet. No significant changes were found in the chronobiological characteristics of epinephrine and norepinephrine with the peak of excretion in the afternoon both during (epinephrine: 16:30 h; norepinephrine: 16:45 h) and after the diet (epinephrine: 17:35 h; norepinephrine: 18:00 h). It seems doubtful that alterations in the chronobiological pattern of catecholamines play a role in the metabolic adaptation occurring during very low calorie diet in obese females.

Chronobiology of catecholamine excretion in normal and diabetic men

The adrenomedullary response to stimuli is often elevated in poorly controlled insulin dependent diabetic patients, and it is controversial whether the adrenomedullary hyperactivity induces the suppression of the circadian rhythm of catecholamines. We have studied the urinary excretion of catecholamines in 11 diabetic patients during 48 h in 4-h collections. Eleven age and weight matched normal subjects served as controls. A circadian rhythm was detected for adrenaline and noradrenaline excretion both in normal and diabetic subjects, with the highest value for both catecholamines in the early afternoon. The mean daily adrenaline levels were significantly higher in diabetic than in control subjects (p less than 0.05). The dopamine excretion was correlated with noradrenaline excretion in normal subjects but did not show a definite circadian rhythm. We conclude that the adrenomedullary hyperactivity does not affect the rhythmic fluctuations of adrenaline and noradrenaline. The dopamine excretion does not show circadian variations and this probably reflects the absence of a single controlling oscillator.

The endocrine effects of visual erotic stimuli in normal men

Endocrine responses to erotic stimulation in the laboratory were assessed in eight normal subjects. Each subject was tested on two occasions. On one occasion only neutral stimuli were involved. After 15 min baseline, 30 min of films were shown. For the erotic condition on the other occasion, two 10-min erotic films were interspersed with 10 min of neutral film. Fifteen-minute blood samples were taken from the start of each test and continued for 5 hr after the films. Plasma was assayed for testosterone, LH, prolactin, cortisol, ACTH and beta-endorphin. Urine was collected for 4 hr before and 4 hr after the films; this was assayed for adrenaline, noradrenaline and dopamine. Sexual arousal occurred in response to the erotic films in all subjects, as shown by erectile and subjective responses. There were no significant changes in hormone or catecholamine levels following either the erotic or the neutral stimuli, except for a rise in cortisol during the neutral but not the erotic film. These results indicate that in the laboratory, substantial sexual response can occur without accompanying endocrine or biochemical changes.