Disparity of autonomic control in type 2 diabetes mellitus

Abstract

Aims/hypothesis: Acute insulinaemia activates the sympathetic drive in a nonuniform manner. The extent and nature of such activation in type 2 diabetic patients who do not have neuropathy have not yet been addressed despite evidence relating sympathetic activation to cardiovascular risk. We planned to determine the magnitude and extent of the sympathetic drive and its reflex responses in patients with type 2 diabetes and fasting hyperinsulinaemia. Methods: We measured resting muscle sympathetic nerve activity (MSNA) as the mean frequency of multiunit bursts and single unit muscle sympathetic nerve activity (s-MSNA) in 17 overweight patients with type 2 diabetes and two matched normal control groups comprising 17 overweight and 16 normal-weight subjects. We also tested the MSNA and s-MSNA responses to cold pressor and isometric hand-grip tests, along with the effect of sympatho-vagal balance on heart period variability. Results: Both MSNA and s-MSNA in the group with type 2 diabetes (66±3.5 bursts/100 beats and 78±4.5 impulses/100 beats) were greater (at least p<0.0001) than in the overweight control group (42±2.6 bursts/100 beats and 48±3.4 impulses/100 beats) and normal-weight control group (43±6.2 bursts/100 beats and 51±7.1 impulses/100 beats), though the three groups had similar reflex responses, baroreflex sensitivity and sympathovagal balance controlling the heart period. Conclusions/ interpretation: The patients with type 2 diabetes had no evidence of impaired reflex or autonomic control of heart period variability at a time when there was central sympathetic activation to the periphery. Furthermore, being overweight itself was not associated with sympathetic activation.

Changes in the salivary protein profile of morbidly obese women either previously subjected to bariatric surgery or not

“…Some studies suggest that obesity is associated with increases [20], whereas weight loss is related to decreases in sympathetic nervous system activity [42]. Thus, the high levels of this protein in group O and the low levels of the protein in group O-BS may partly reflect the activity of this branch of the autonomic nervous system.…”

Association between nocturnal blood pressure dipping and insulin metabolism in obese adolescents

“…However, it has been suggested that the presence of hyperinsulinemia and insulin resistance increases sympathetic nerve activity. 22 Also, C-peptide, a cleavage product of proinsulin, Blood pressure dipping and insulin metabolism M Westerståhl and C Marcus might induce the proliferation of vascular smooth muscles, 23 leading to alterations in arteriolar structure and function. In this study, we observed a very high prevalence, approximately 50%, of non-dipping among severely obese adolescents.…”

Sympathetic nervous system behavior in human obesity

“…However, the results of one study suggest that MSNA may not be elevated in overweight humans (Huggett et al, 2005). In addition, whether the higher MSNA observed in obese individuals is genetically determined and, perhaps, part of a phenotype that is evident prior to significant weight gain and obesity is not clear.…”

“…The results of numerous studies indicate that obese humans demonstrate ∼50-100% higher levels of MSNA compared with their non-obese peers (Spraul et al, 1993, Scherrer et al, 1994, Spraul et al, 1994, Gudbjornsdottir et al, 1996, Grassi et al, 2000, Weyer et al, 2000, Alvarez et al, 2002. In contrast, Hugget et al (Huggett et al, 2005) reported that MSNA was not elevated in overweight individuals. The reason(s) for this apparent discrepancy is not entirely clear but could be due, in part, to the selection of a group of overweight subjects with a primarily subcutaneous obese phenotype (see below under "6.…”