Elisabeth A Lambert | PubMed Health

PubMed2005

Effects of dietary weight loss on sympathetic activity and cardiac risk factors associated with the metabolic syndrome.

CONTEXT: Weight reduction, the first line treatment for the metabolic syndrome, improves insulin sensitivity and associated metabolic and cardiovascular abnormalities, but there is a paucity of data regarding its effect on sympathetic nervous system (SNS) activity in this clinical setting. OBJECTIVES: The objectives of this study were to test the hypothesis that dietary weight loss attenuates both insulin resistance and SNS activity and to examine the relationships between SNS activity and metabolic syndrome (MetS) components. DESIGN: This was a single-sample, repeated measures design study. SETTING: This study was performed at a tertiary referral center. PARTICIPANTS: Twenty-three MetS subjects (age, 58 +/- 2 yr; body mass index, 33.3 +/- 0.8 kg/m2; mean +/- sem) were studied. INTERVENTION: A hypocaloric modified Dietary Approaches to Stop Hypertension diet (26% fat, 22% protein, and 51% carbohydrate; 100 mmol/d sodium) was consumed for 3 months. MAIN OUTCOME MEASURES: The main outcome measures were postganglionic muscle sympathetic nerve activity (microneurography at a peroneal nerve), whole-body plasma norepinephrine spillover rate, spontaneous cardiac baroreflex function, and insulin sensitivity. RESULTS: The hypocaloric diet significantly reduced body weight by 7% and improved all MetS components. Norepinephrine spillover decreased from 877 +/- 180 to 503 +/- 39 ng/min (P = 0.005), and muscle sympathetic nerve activity decreased from 40.6 +/- 2.1 to 34.6 +/- 2.4 bursts/min (P = 0.01), whereas cardiac baroreflex sensitivity increased by 23.0 +/- 8.0% (P = 0.02). The change in the norepinephrine spillover rate correlated positively and independently with the change in plasma leptin concentration (r = 0.49; P = 0.03). CONCLUSION: Weight loss by a hypocaloric diet with moderate sodium restriction diminishes SNS activity in MetS subjects. This may be due to the consequences of decreased leptin concentration, enhanced insulin sensitivity, or improvements in cardiac baroreflex function.

Aged↗

PubMed2002

Sympathetic and cardiac baroreflex function in panic disorder.

BACKGROUND: Recent reports have demonstrated increased cardiac risk, and an association with essential hypertension in patients with panic disorder. The cause is not known, but possibly involves sympathetic nervous activation. In this study, we evaluated the arterial baroreflex control of vascular sympathetic nervous outflow and cardiac baroreflex function in panic disorder patients. METHODS AND RESULTS: We studied nine patients suffering from panic disorder and ten healthy subjects. Microneurographic recording of muscle sympathetic nerve activity (MSNA) was made with simultaneous recording of blood pressure (BP) and electrocardiogram (ECG). The relationship between MSNA and spontaneous diastolic BP (DBP) changes was assessed at rest and was defined as the arterial baroreflex control of MSNA. Cardiac baroreflex function was assessed using the sequence method. Anxiety was assessed using Spielberger's anxiety state and trait inventory. The slopes of the relationship between MSNA and DBP were more negative (steeper) in the panic disorder group compared with the control subjects (-5.97 +/- 0.45 versus -3.06 +/- 0.43 bursts/100 heart beats per mmHg, P < 0.001). Panic disorder patients had significantly higher state and trait anxiety scores. The slope of the relationship between MSNA and diastolic BP was significantly related to the trait anxiety of the subjects. There was no difference between the cardiac baroreflex sensitivity between the two groups. CONCLUSION: Patients with panic disorder exhibit enhanced reflex gain of the arterial baroreflex control of MSNA but no change in the cardiac baroreflex. While any clinical significance this observation might have in relation to increased cardiac risk in panic disorder, or to concordance with essential hypertension, remains to be elucidated, increased reactivity of vasoconstricting sympathetic nerves may be a trait characteristic in this cohort.

Adult↗