Effect of parathyroidectomy on osteopontin and undercarboxylated osteocalcin in patients with primary hyperparathyroidism

PURPOSE

Surgical treatment for primary hyperparathyroidism (PHPT) improves bone metabolism. Osteocalcin (OC) and its undercarboxylated form (ucOC) are associated with bone and energy metabolism. Osteopontin (OPN), a multifunctional protein expressed in bone, is involved in resorption, along with β-carboxyl-terminal cross-linking telopeptide of type 1 collagen (β-CTX), and osteoprotegerin (OPG). Our aim was to investigate these biomarkers of bone metabolism in patients with PHPT.

METHODS

We examined 30 individuals with PHPT, in a clinical research facility, before and 1 month following parathyroidectomy. Circulating levels of OC, ucOC, OPN, β-CTX, and OPG were examined as bone biomarkers along with inflammatory markers (e.g., interleukin-6 [IL-6], lipocalin-2), insulin resistance (i.e., homeostasis model assessment for insulin resistance [HOMA-IR]), adiposity (i.e., leptin, adiponectin), PTH, calcium, 25-hydroxyvitamin D, creatinine, and demographics.

RESULTS

Participants (27 females/3 males) were 60 ± 9 (mean±SD) years old. There was a significant reduction of ucOC (7.9 ± 5.1 [median±SIQR] vs. 6.6 ± 3.7 ng/mL, p = 0.022) and OPN (75.4 ± 14.5 vs. 54.5 ± 9.2 ng/mL, p < 0.001) pre- versus post-parathyroidectomy. There were no univariate differences postoperatively for IL-6, HOMA-IR, leptin, or adiponectin. Regression analysis showed that postoperative levels of adiponectin, IL-6, and OPN were significantly associated with ucOC, while adjusting for PTH and albumin corrected calcium levels (model R² = 0.610, p = 0.001). With OPN as the dependent variable, higher adiponectin and lower ucOC were significantly associated with lower OPN levels postoperatively (model R² = 0.505, p = 0.010).

CONCLUSION

The lower 1-month postoperative OPN and ucOC levels in PHPT seem to indicate reduced bone resorption. Decreased ucOC levels may also suggest lower energy demands postoperatively.

Pre-heparin lipoprotein lipase mass as a potential mediator in the association between adiponectin and HDL-cholesterol in type 2 diabetes

AIM

Lipoprotein lipase (LPL) is a major enzyme in lipid metabolism. Dyslipidemia, characterized by decreased high-density lipoprotein cholesterol (HDL-C), is prevalent in persons with type 2 diabetes mellitus (T2DM). The aim of this study was to determine whether pre-heparin LPL mass mediates the association between adiponectin and HDL-C in individuals with T2DM.

METHODS

Pre-heparin LPL mass was measured via an enzyme-linked immunosorbent assay, adiponectin by radioimmunoassay, and HDL-C was determined enzymatically. Participants' (n = 50) demographics, HbA1c, adiposity, homeostasis model assessment for insulin resistance (HOMA-IR), serum creatinine, and lipids were measured. Path analysis was utilized to test whether pre-heparin LPL mass is a mediator in the relationship between adiponectin and HDL-C.

RESULTS

All four criteria for mediation were satisfied in the path analysis. The indirect effect of adiponectin on HDL-C through pre-heparin LPL mass was significant, p = 0.001, whereas the direct effect of adiponectin on HDL-C was not significant, p = 0.074. These results remained consistent even after adjustments for age, gender, body mass index, HOMA-IR, and serum creatinine in the model.

CONCLUSION

The findings in this study suggest that pre-heparin LPL mass may mediate the association between adiponectin and HDL-C in T2DM. This relationship for measures of HDL-C functionality requires future investigation.

Osteopontin and clusterin levels in type 2 diabetes mellitus: differential association with peripheral autonomic nerve function

Osteopontin (OPN) and clusterin are secreted glycoproteins potentially associated with nerve function. Sudomotor dysfunction is associated with the development of foot ulcerations. The purpose of this study was to investigate the potential relationship of OPN and clusterin with sudomotor function (i.e., autonomic nerves that control sweating) in participants with type 2 diabetes mellitus (T2DM). Sudomotor function was assessed using SUDOSCAN® which measures electrochemical skin conductance (ESC) of the hands and feet. Demographics (e.g., age, gender, race, body mass index (BMI)), HbA1c, 25-hydroxyvitamin D, creatinine, OPN, and clusterin were also determined for the participants. Fifty individuals with T2DM (age = 59±11 years; 23/27 male/female; 13 African Americans) participated in this study. Lower ESC for the hands and feet were observed in African Americans versus Caucasians/Asians (p < 0.05). No significant ESC differences were observed for good [HbA1c <7%] versus poor [HbA1c ≥7%] glycemic control. With regard to gender, ESC values were lower for the hands for females (p < 0.05). In linear regression with ESC for the hands or feet as the dependent variable, increased OPN levels, but not clusterin, were independently associated with reduced sudomotor function while adjusting for age, gender, race, BMI, and glycemic control (ESC hands model R 2 = 0.504, p < 0.001; ESC feet model R 2 = 0.534, p < 0.001). The association between OPN and reduced sudomotor function found in our study warrants further investigation to delineate the underlying mechanisms and determine if OPN is neuroprotective, involved in the pathogenesis of sudomotor dysfunction, or simply a bystander.

Osteoprotegerin is a Better Serum Biomarker of Coronary Artery Calcification than Osteocalcin in Type 2 Diabetes

OBJECTIVE

Coronary artery calcification (CAC) is a prominent feature of atherosclerosis and is associated with cardiovascular events. In vitro studies have suggested that osteoprotegerin (OPG) and osteocalcin (OC) exert anticalcification potential in the vessel wall. The objective of this study was to investigate the association of CAC and serum bone biomarkers in persons with type 2 diabetes.

METHODS

We examined 50 individuals with type 2 diabetes. CAC imaging was performed by multidetector computed tomography. CAC scores ≥10, expressed in Agatston units, were considered abnormal. OC, undercarboxylated OC (ucOC), and OPG levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Abnormal CAC scores were found for 64% of the study cohort. OPG levels were significantly elevated (5.5 ± 2.0 pmol/L vs. 4.2 ± 1.7 pmol/L; P = .026) for those with abnormal CAC scores. No univariate differences were found for OC or ucOC. Logistic regression analyses revealed that an increase in serum OPG level was significantly associated with an increase in CAC score (odds ratio, 3.324; 95% confidence interval, 1.321 to 8.359; P = .011). Longer duration of diabetes was a significant covariate (P = .026), whereas nonsignificant covariates in the final model were age, gender, systolic blood pressure, body mass index, insulin resistance determined by the homeostasis model assessment for insulin resistance, leptin, adiponectin, and glycemic control. The Nagelkerke R2 for the model was 0.66. Neither OC nor ucOC were significantly associated with elevated CAC scores.

CONCLUSION

Our results suggest that OPG is a more useful serum biomarker than OC or ucOC for identifying those at increased risk of arterial calcification in type 2 diabetes.

Vitamin D Insufficiency is Associated with Reduced Parasympathetic Nerve Fiber Function in Type 2 Diabetes

OBJECTIVE

Vitamin D insufficiency is prevalent in subjects with type 2 diabetes mellitus (T2DM) and is associated with peripheral neuropathy. However, there are little data regarding vitamin D status in patients with cardiovascular autonomic neuropathy. Our objective was to evaluate the association of cardiovascular autonomic function, 25-hydroxyvitamin D (25[OH]D) insufficiency (i.e., levels <30 ng/mL), and multiple metabolic parameters in subjects with T2DM.

METHODS

We examined 50 individuals with T2DM. Cardiovascular autonomic function (i.e., parasympathetic function) was assessed by RR-variation during deep breathing (i.e., mean circular resultant [MCR] and expiration/inspiration [E/I] ratio). Metabolic parameters included measures of adiposity, glycemic control, insulin resistance, calcium metabolism, and 25(OH)D.

RESULTS

Participants with 25(OH)D insufficiency (n = 26) were younger (66 ± 9 vs. 60 ± 10 years, P<.05), more insulin resistant, had a higher body mass index (BMI) and lower adiponectin levels. The MCR (39.5 ± 26.3 vs. 27.6 ± 17.2, P<.01) and E/I ratio (1.21 ± 0.17 vs. 1.15 ± 0.09, P<.01) were lower for those with 25(OH)D insufficiency after controlling for age. A stepwise selection procedure regressing MCR and E/I ratio on a number of metabolic parameters resulted in a model identifying age and 25(OH)D insufficiency as significant determinants for both measures. The interaction of age x 25(OH)D insufficiency was also included (MCR model, R2 = 0.491, P<.001; E/I ratio, R2 = 0.455, P<.001). Neither glycemic control nor other metabolic parameters were selected.

CONCLUSION

Our results suggest that 25(OH)D insufficiency is associated with reduced parasympathetic function, with a stronger association in younger persons with T2DM. Studies are needed to determine if vitamin D supplementation into the sufficient range could prevent or delay the onset of cardiovascular autonomic dysfunction.

Osteopontin and osteoprotegerin levels in type 2 diabetes and their association with cardiovascular autonomic function

AIMS

Osteopontin (OPN) and osteoprotegerin (OPG) are bone metabolism biomarkers potentially associated with nerve function. We evaluated the association of cardiovascular autonomic nerve function, OPN, and OPG in 50 individuals with type 2 diabetes mellitus (T2DM).

METHODS

RR-variation during deep breathing (i.e., mean circular resultant (MCR) and expiration/inspiration (E/I) ratio) was used to assess parasympathetic nerve function. Participants' demographics, HbA1c, 25-hydroxyvitamin D (25(OH)D), BMI, HOMA-IR, calcium, parathyroid hormone, creatinine, OPN, and OPG were determined.

RESULTS

Using stepwise multiple linear regression analysis with MCR or E/I ratio as the dependent variable, OPN was independently associated with reduced autonomic function. A previous report showed a significant association of cardiovascular autonomic function with age, 25(OH)D insufficiency, and the interaction of age×25(OH)D insufficiency. Here we report a novel association for OPN and its interaction with age indicating that for those who are younger, elevated OPN levels are related to a greater loss of autonomic function (MCR model R2=0.598, p<0.001; E/I model R2=0.594, p<0.001).

CONCLUSION

Our results suggest that OPN is associated with reduced parasympathetic function, particularly in younger individuals with T2DM. Further studies are needed to determine if OPN is neuroprotective, involved in the pathogenesis of autonomic dysfunction, or a bystander.

Autonomic modulation in gestational diabetes mellitus

AIMS

The aim of this study was to evaluate the influence of gestational diabetes mellitus (GDM) and positional aortocaval compression on cardiovascular autonomic nervous system (ANS) function in late pregnancy.

METHODS

Pregnant women with (n=31) and without (n=12) GDM were evaluated at 30-35weeks gestation and 2-3months postpartum. Measures of ANS function included power spectral analysis (performed sitting) and RR-variation during deep breathing (performed supine). Time-related changes (late pregnancy versus 2-3months postpartum) for measurements of cardiovascular ANS function were analyzed using multivariate analysis of variance for repeated measures.

RESULTS

Baseline characteristics were similar for both groups. Comparing ANS measures for GDM+versus GDM- women during pregnancy and postpartum revealed no significant differences. Time related changes indicated that during late pregnancy total spectral power, low frequency (LF) power, high frequency (HF) power, and RR-variation during deep breathing were significantly reduced (p<0.001 for all). The LF/HF ratio, however, was not significantly affected during late pregnancy (p=0.678).

CONCLUSIONS

Our results suggest decreased activity in both branches of the ANS during mid-third trimester pregnancy, but no significant change in sympathovagal balance. Aortocaval compression appears to affect ANS function whether tests were performed sitting or supine for GDM+and GDM- women.

Screening blood donors for diabetes: analysis of use, accuracy, and cost

BACKGROUND

The objective was to determine if a free, voluntary diabetes screening program as a part of the blood donation process might be cost-effective.

STUDY DESIGN AND METHODS

During the first 6 months of the program, 26,415 donors were screened using a single random plasma glucose (RPG) level. All donors were asked to eat before donation. Low-, moderate-, and high-risk groups were formed based on RPG levels (<140, 140-200, and >200 mg/dL). Contact with a telephone questionnaire was made with 139 of 178 (78%) of the persons in the high-risk group with 33 new cases of diabetes diagnosed by the donor's physician and 26 donors indicating that they were not diagnosed with diabetes. Sex- and age-matched donors in the low- and moderate-risk groups were contacted and administered the same questionnaire.

RESULTS

The three risk groups were similar, except for body mass index (28.1 ± 5.4 kg/m2 vs. 29.9 ± 5.5 kg/m2 vs. 32.7 ± 5.6 kg/m2 , p < 0.001). The discriminative effectiveness of screening was evaluated by the area under the receiver operating characteristics (AROC) curve. The AROC curve was 0.950 (95% confidence interval, 0.920-0.979) for the identification of diabetes. Using a RPG cutoff of 200 mg/dL, sensitivity was 100%, specificity was 82%, and positive predictive value was 56%. Cost analyses showed that the mean cost to screen, per donor, was less than $1. Cost per case identified was estimated to be less than $500 for a RPG cutoff of 200 mg/dL.

CONCLUSIONS

Screening during the blood donation process appears to be accurate, convenient, and inexpensive.

Direct renin inhibition improves parasympathetic function in diabetes

AIM

The renin-angiotensin-aldosterone system (RAAS) and autonomic nervous system regulate the cardiovascular system. Blockade of the RAAS may slow the progression of end-organ damage. Direct renin inhibition offers a means for blocking the RAAS. The objective of this study was to examine the effect of direct renin inhibition on cardiovascular autonomic function.

METHODS

In this double-blind, placebo-controlled trial, 60 individuals with diabetes were randomly assigned to 300 mg of aliskiren or placebo once daily for 6 weeks. The primary end point was a change in tests of cardiovascular autonomic function. Autonomic function was assessed by power spectral analysis and RR-variation during deep breathing [i.e. mean circular resultant (MCR), expiration/inspiration (E/I) ratio]. The MCR and E/I ratio assess parasympathetic function. Secondary measures included change in biochemical parameters [e.g. plasma renin activity, leptin and interleukin-6]. Change in cardiovascular autonomic function and blood analytes were analysed by a mixed effects model for repeated measures.

RESULTS

Baseline characteristics were similar between treatment groups. In response to aliskiren compared with placebo, blood pressure was reduced as well as plasma renin activity [from 2.4 ± 3.8 (mean ± standard deviation) to 0.5 ± 0.4 µg/l/h, p < 0.001]. There was a significant interaction (aliskiren × visit) for MCR (p = 0.003) and E/I ratio (p = 0.003) indicating improvement in MCR and E/I ratio for those on aliskiren. MCR means, baseline vs. follow-up, were 41.8 ± 19.7 vs. 50.8 ± 26.1 (aliskiren) and 38.2 ± 23.6 vs. 37.5 ± 24.1 (placebo).

CONCLUSIONS

Parasympathetic function (i.e. MCR and E/I ratio) was enhanced by downregulation of the RAAS.

Hip strength in adults with type 1 diabetes is associated with age at onset of diabetes

We investigated the association of age at onset of type 1 diabetes with areal bone mineral density (aBMD), estimates of bone strength, and outer diameter. Using dual-energy X-ray absorptiometry (DXA), aBMD, axial strength (cross-sectional area [CSA]), bending strength (section modulus [SM]), and outer diameter at the narrow neck, intertrochanter, and shaft of the proximal femur were determined for 60 adults. Analysis of covariance (ANCOVA) was used to determine if the DXA-based measures of bone were related to age at onset and if this relationship differed by gender. Age at onset, gender, and the interaction of age at onset by gender were included in the ANCOVA models along with current age, duration, height, lean soft tissue mass, and hemoglobin A1c as covariates. In the adjusted models with CSA, SM, or outer diameter as the dependent variable, age at onset (p<0.01) and gender (p<0.0001) were significant with no interaction. For shaft aBMD, there was a significant age at onset by gender interaction (p=0.0285), where an earlier onset was associated with lower aBMD in the femoral shaft of females but not males. The findings suggest that an earlier onset of type 1 diabetes is associated with lower measures of bone strength and outer diameter.

Effects of surgically induced weight loss by Roux-en-Y gastric bypass on cardiovascular autonomic nerve function

BACKGROUND

Obesity is associated with autonomic imbalance. With respect to cardiovascular autonomic dysfunction, this is characterized by reduced heart rate variability (HRV). Our objective was to determine the effect of surgically induced weight loss on cardiovascular autonomic nerve fiber function in subjects with severe obesity and examine whether an association with reduced insulin resistance exists. The setting was a hospital and private practice in the United States.

METHODS

A total of 32 morbidly obese patients (body mass index 51 ± 11 kg/m(2)) underwent laparoscopic Roux-en-Y gastric bypass. Measures of HRV (e.g., power spectral analysis, RR variation during deep breathing) were used to evaluate autonomic function before and 6 months after surgery. The homeostasis model assessment of insulin resistance index (HOMA-IR) was used to assess insulin resistance.

RESULTS

At 6 months after bariatric surgery, the patients had lost 58% excess body mass index with improvement in the HOMA-IR (3.0 ± 1.4 versus 1.1 ± .7; P < .001). Measures of RR variation during deep breathing and total spectral power, low frequency (LF) power (influenced by sympathetic and parasympathetic activity), and high frequency (HF) power (parasympathetic activity) increased with weight loss. The LF/HF ratio was lower (1.5 ± 1.5 versus .9 ± .7, P < .05) with a reduction in weight. Spectral analysis of HRV combined with spectral analysis of respiratory activity generated the respiration frequency area (RFA) and low frequency area. The RFA was increased, and the LFA/RFA ratio was reduced with weight loss. HOMA-IR and HRV did not correlate.

CONCLUSION

Surgically induced weight loss has a favorable effect on autonomic function, but it does not appear to be directly attributable to reduced insulin resistance.

Autonomic imbalance: prophet of doom or scope for hope?

It has long been recognized that cardiac autonomic neuropathy increases morbidity and mortality in diabetes and may have greater predictive power than traditional risk factors for cardiovascular events. Significant morbidity and mortality can now be attributable to autonomic imbalance between the sympathetic and parasympathetic nervous system regulation of cardiovascular function. New and emerging syndromes include orthostatic tachycardia, orthostatic bradycardia and an inability to use heart rate as a guide to exercise intensity because of the resting tachycardia. Recent studies have shown that autonomic imbalance may be a predictor of risk of sudden death with intensification of glycaemic control. This review examines an association of autonomic dysregulation and the role of inflammatory cytokines and adipocytokines that promote cardiovascular risk. In addition, conditions of autonomic imbalance associated with cardiovascular risk are discussed. Potential treatment for restoration of autonomic balance is outlined.

Autonomic nerve fiber function and bone mineral density in individuals with type 1 diabetes: a cross-sectional study

AIMS

Experimental models support a role for the sympathetic nervous system in bone metabolism. Beta-adrenoreceptors have been demonstrated on osteoblast-like cells. Beta-blocker use is associated with higher bone mineral density (BMD) in some epidemiologic studies. The aim of this study was to determine if measures of the autonomic nervous system (ANS) were associated with reduced BMD in type 1 diabetes.

METHODS

We studied 66 individuals with type 1 diabetes. Dual-energy X-ray absorptiometry was used to measure BMD and bone mineral content (BMC). Measures of heart rate variability (HRV) (e.g., power spectral analysis, mean circular resultant) and circulating norepinephrine levels were used to evaluate autonomic function.

RESULTS

BMD/BMC were examined by gender for individuals with a normal versus elevated low-frequency (LF) band (expressed in normalized units). No significant differences in BMD/BMC were shown for individuals with an elevated LF band. Direct-entry linear regression models with BMD/BMC as the dependent variable were performed. Duration, gender, BMI, HbA(1c), insulin dose/kg, activity energy expenditure, and measures of HRV were entered as potential independent variables. No measures of HRV, or norepinephrine, were independently associated with BMD/BMC.

CONCLUSIONS

The ANS, as assessed by measures of HRV, does not appear to impact BMD/BMC in type 1 diabetes.

Zinc intake and biochemical markers of bone turnover in type 1 diabetes

OBJECTIVE

To examine the relationship between Zn nutritive status and biochemical markers of bone turnover in type 1 diabetes.

RESEARCH DESIGN AND METHODS

Serum osteocalcin, urine N-telopeptides, and dietary intake data, obtained by 3-day food records, were assessed for 66 individuals with type 1 diabetes.

RESULTS

Zn intake correlated with osteocalcin in the group overall (r = 0.48; P < 0.001) but not with N-telopeptides. Examined by sex, both Zn and osteocalcin correlated for men (r = 0.57; P < 0.001), but the correlation did not reach statistical significance for women (r = 0.34; P = 0.09). A direct-entry linear regression model with osteocalcin as the dependent variable was performed. Duration, sex, A1C, insulin use per kilogram, total calorie intake, and Zn intake were entered as potential independent variables. The model was statistically significant (R(2) = 0.32; P < 0.01). Zn intake (P < 0.001), however, was the only independent correlate of osteocalcin.

CONCLUSIONS

This study provides evidence of a positive relationship between Zn intake and osteocalcin in type 1 diabetes.

Continuous positive airway pressure therapy improves cardiovascular autonomic function for persons with sleep-disordered breathing

BACKGROUND

Sleep-disordered breathing (SDB) is an independent risk factor for cardiovascular morbidity. Dysfunction of the cardiovascular autonomic nervous system may be a potential mechanism whereby SDB is linked to cardiovascular disease. Repetitive sympathetic activation during apneic episodes may impair cardiovascular reflex function, and increased sympathetic activity can stimulate renin release. Given that patients with SDB may have reduced cardiovascular autonomic function, the purpose of this study was to determine whether treatment with continuous positive airway pressure (CPAP) for 6 weeks would improve autonomic function.

METHODS

Twenty-nine participants with a diagnosis of SDB, who completed 6 weeks of CPAP therapy, were evaluated for cardiovascular autonomic nerve fiber function at baseline and post therapy. Autonomic function tests included the following: R-R interval variation during deep breathing measured by vector analysis (ie, mean circular resultant [MCR]) and expiration/inspiration (E/I) ratio; and the Valsalva maneuver. Participants were also evaluated prior to CPAP therapy for plasma renin activity levels.

RESULTS

Participants in this study showed improved cardiovascular autonomic function after 6 weeks of treatment (baseline vs follow-up) as assessed by the mean (+/- SD) MCR (33.2 +/- 22.5 vs 36.9 +/- 24.2, respectively; p < 0.05) and E/I ratio (1.20 +/- 0.12 vs 1.24 +/- 0.14, respectively; p < 0.01). Improved vagal tone was also noted for subjects with elevated renin levels.

CONCLUSIONS

Treatment of SDB with CPAP for 6 weeks improved vagal tone and may be beneficial in reducing the risk of developing clinical manifestations of cardiovascular autonomic dysfunction (eg, increased risk of mortality).

An overview of the effect of weight loss on cardiovascular autonomic function

The prevalence of obesity is rising to epidemic proportions in many countries worldwide. Obesity seriously increases an individual's risk of developing many health problems including diabetes. Diabetes, like obesity, is also in epidemic proportions with 300 million adults predicted to have the disease by 2025. Investigating strategies for the prevention and treatment of obesity and diabetes is vitally important. Autonomic dysfunction is evident in both obesity and diabetes. In persons with diabetes, impaired cardiovascular autonomic activity is characterized by a reduction in parasympathetic tone with a relative increase in sympathetic activity and is specifically associated with a number of clinically significant manifestations including exercise intolerance, intraoperative cardiovascular lability, orthostatic hypotension, silent myocardial ischemia, and increased risk of mortality. In obesity, parasympathetic function is decreased while regional heterogeneity of increased sympathetic activity may occur. Autonomic dysfunction increases cardiovascular workload, hemodynamic stress, serious dysrhythmias, and significant cardiac pathology. Thus, cardiac autonomic imbalance may also be an important link between obesity and increased morbidity and mortality. Beyond the obese and diabetic state, multiple variables associated with these conditions such as insulin, glucose, leptin, adiponectin and free fatty acids have an affect on the autonomic nervous system. Autonomic disturbances, however, appear to be reversible with weight reduction. Since autonomic imbalance is a marker of adverse risk, improvement obtained from weight loss should be beneficial for the health of individuals with obesity and diabetes. This overview will examine the relationship of the autonomic nervous system in obesity and diabetes and explore the effect of weight loss on autonomic function.

Impact of surgically induced weight loss on cardiovascular autonomic function: one-year follow-up

OBJECTIVE

To determine the impact of surgically induced weight loss on cardiovascular autonomic function in subjects with severe obesity and examine whether the effect was comparable for persons with and without diabetes.

RESEARCH METHODS AND PROCEDURES

Twenty-six severely obese individuals (BMI = 48 +/- 7 kg/m(2)) underwent bariatric surgery (laparoscopic Roux-en-Y gastric bypass, n = 21; laparoscopic adjustable gastric banding, n = 5). Cardiovascular autonomic function (heart rate variation during deep breathing and the Valsalva maneuver) was assessed before and 6 and 12 months after surgery.

RESULTS

Twelve months after bariatric surgery, there was a 28% decrease in BMI. There was an increase in all parasympathetic indices of autonomic function (all assessment modalities, p < 0.05) with weight loss. The amount of improvement from baseline for all measures of autonomic function did not differ for those with or without diabetes.

DISCUSSION

Surgically induced weight loss 12 months after surgery has a favorable effect on cardiovascular autonomic function in severely obese individuals with and without diabetes.

Preserved autonomic function in amenorrheic athletes

Reproductive hormones such as estradiol and progesterone are known to influence autonomic cardiovascular regulation. The purpose of this study was to determine whether amenorrheic athletes (AA) have impaired autonomic cardiovascular regulation compared with eumenorrheic athletes (EA). Thirty-five athletes were tested: 13 AA (19 +/- 1 yr), 13 EA (21 +/- 1 yr), and 9 EA (23 +/- 1 yr) on oral contraceptives (EA-OC). Multiple indexes of autonomic cardiovascular regulation were assessed: respiratory sinus arrhythmia (RSA), cardiovagal baroreflex sensitivity (BRS) via phase IV and phase II of the Valsalva maneuver, a spontaneous index of BRS, and the heart rate and blood pressure responses to orthostatic stress (20-min 60 degrees head-up tilt). RSA was not different among the groups. There were no group differences in the spontaneous index of BRS (AA = 30 +/- 6, EA = 24 +/- 3, EA-OC = 29 +/- 5 ms/mmHg) or in phase II (AA = 8 +/- 2, EA = 7 +/- 1, EA-OC = 8 +/- 1 ms/mmHg) of the Valsalva. There was a difference in BRS during phase IV (AA = 21 +/- 3, EA = 15 +/- 1, EA-OC = 26 +/- 6 ms/mmHg; ANOVA P = 0.04). Tukey's post hoc test indicated that BRS was greater in the EA-OC group compared with the EA group (P = 0.04). There were no differences in cardiovascular responses to orthostatic stress among the groups. In conclusion, AA do not display signs of impaired autonomic function and orthostatic responses compared with EA or EA-OC during the follicular phase of the menstrual cycle.

Cardiovascular autonomic neuropathy due to diabetes mellitus: clinical manifestations, consequences, and treatment

CONTEXT

The aim of this article was to review the importance of the clinical identification of persons with cardiovascular autonomic neuropathy (CAN) and discuss potential treatment interventions.

EVIDENCE ACQUISITION

A MEDLINE search was conducted for articles published during the last 20 yr. In addition, subsequent references of retrieved articles were reviewed. Search strategies included using key terms such as CAN, heart rate variability, orthostatic hypotension, and diabetes mellitus.

EVIDENCE SYNTHESIS

CAN is a common form of diabetic autonomic neuropathy and causes abnormalities in heart rate control as well as central and peripheral vascular dynamics. The clinical manifestations of CAN include exercise intolerance, intraoperative cardiovascular lability, orthostatic hypotension, painless myocardial ischemia, and increased risk of mortality. CAN contributes to morbidity, mortality, and reduced quality of life for persons with diabetes. The American Diabetes Association has recently published a statement that provides guidelines for prevention, detection, and management of neuropathy, including CAN, for healthcare providers who care for patients with diabetes. Algorithms for the evaluation and treatment of the patient with CAN, even if the patient is asymptomatic, are provided in this review.

CONCLUSIONS

Once CAN is identified in a patient with diabetes, healthcare providers may consider altering the prescribed exercise regimen, increasing surveillance for cardiac ischemia, carefully reexamining the list of prescribed medications, and aggressively treating cardiovascular risk factors (e.g. hypertension) that may be associated with the development of CAN.