The metabolically healthy but obese postmenopausal woman presents a favourable heart rate variability profile

AGING, HEART RATE VARIABILITY AND METABOLIC IMPACT OF OBESITY

The relationship between aging and changes in heart rate variability (HRV) could depend on the metabolic profile of obese people, i.e. metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO). We aimed to determine the age at which obesity related autonomic dysfunction becomes significant and whether it decreases differently according to metabolic profile. We analyzed HRV in 99 adults using Wildman's criteria for metabolic profile and 5-minute HRV for autonomic nervous system. In MHO, high frequency (HF) decreased in the 4^th decade of life. In MUO, standard deviation of R-R intervals (SDNN), root mean square of successive differences of all R-R intervals (RMSSD), number of adjacent intervals differing by more than 50 ms expressed as percentage of all intervals in the collecting period (pNN50), HF, low frequency (LF), LF/HF (LF divided by HF) and total power (TP) decreased in the 4^th decade of life (partial shared variance 28%-36%). In conclusion, an age dependent decrease of HRV occurs in MUO between the third and fifth decade of life. In MHO, HF significantly decreases around the age of 40 years. Cardiometabolic profile influences metabolic aging, altering the autonomic nervous system.

Clinical implication of body size phenotype on heart rate variability

We compared heart rate variability (HRV) values according to the following body size phenotypes: metabolically healthy normal weight (MHNW), metabolically unhealthy but normal weight (MUNW), metabolically healthy but obese (MHO), and metabolically unhealthy obese (MUO). We retrospectively analyzed a dataset from 1200 participants who had visited the Cardiovascular Center at Korea University Guro Hospital between March 2009 and February 2014 and underwent Holter monitoring for 24h. HRV was calculated from standard deviation of normal-to-normal R-R intervals (SDNN), standard deviation of the average normal-to-normal intervals (SDANN), and root mean square of successive differences (rMSSD) measurements, and study subjects were classified according to body mass index (BMI) and presence or absence of metabolic syndrome. Various HRV indices, including SDNN, SDANN, and rMSSD, were significantly lower in MUNW subjects than in MHNW or MHO subjects, while there were no significant differences between MUNW and MUO subjects. Although BMI had no significant correlation with any HRV indices, SDNN, SDANN, and rMSSD values had significant negative correlations with waist circumference and levels of C-reactive proteins, AST, ALT, fasting glucose, and HOMA-IR. A significant positive correlation was observed between HRV index and HDL level. Furthermore, the SDNN value significantly decreased with an increase in the number of metabolic syndrome components after adjusting for other covariates. Compared to MHNW or MHO subjects, Korean men and women with the MUNW phenotype exhibited decreased HRV, suggesting that low HRV is related to adverse cardiovascular outcomes in MUNW individuals.

Obesity and Cardiovascular Disease

The prevalence of obesity has increased worldwide over the past few decades. In 2013, the prevalence of obesity exceeded the 50% of the adult population in some countries from Oceania, North Africa, and Middle East. Lower but still alarmingly high prevalence was observed in North America (≈30%) and in Western Europe (≈20%). These figures are of serious concern because of the strong link between obesity and disease. In the present review, we summarize the current evidence on the relationship of obesity with cardiovascular disease (CVD), discussing how both the degree and the duration of obesity affect CVD. Although in the general population, obesity and, especially, severe obesity are consistently and strongly related with higher risk of CVD incidence and mortality, the one-size-fits-all approach should not be used with obesity. There are relevant factors largely affecting the CVD prognosis of obese individuals. In this context, we thoroughly discuss important concepts such as the fat-but-fit paradigm, the metabolically healthy but obese (MHO) phenotype and the obesity paradox in patients with CVD. About the MHO phenotype and its CVD prognosis, available data have provided mixed findings, what could be partially because of the adjustment or not for key confounders such as cardiorespiratory fitness, and to the lack of consensus on the MHO definition. In the present review, we propose a scientifically based harmonized definition of MHO, which will hopefully contribute to more comparable data in the future and a better understanding on the MHO subgroup and its CVD prognosis.

HEART RATE VARIABILITY IN METABOLICALLY HEALTHY AND METABOLICALLY UNHEALTHY OBESE PREMENOPAUSAL WOMEN

Content

Metabolically healthy obese (MHO) individuals are characterized by absence of metabolic syndrome. The role of autonomic nervous system in metabolic profile of obese subjects has not been sufficiently investigated.

Objective

We analyzed heart rate variability (HRV) in MHO and metabolically unhealthy obese (MUO) premenopausal women.

Design

In 42 women metabolic profile was defined as MHO and MUO.

Subjects and Methods

For metabolic profile Wildman, IDF and HOMA-IR criteria were used. Autonomic nervous system activity was assessed by analysis of heart rate variability.

Results

There was no significant difference in HRV between MHO and MUO premenopausal women. In Wildman division, after adjustment for systolic blood pressure, RRNN and LF/HF were statistically different between groups (p=0.0001; p=0.029). In IDF division, adjusting for waist circumference, LF was significantly different between groups (p=0.004). In HOMA division, adjusting for HOMA, groups were different in SDNN (p=0.009), RMSSD (p=0.002), pNN50 (p=0.003), HF(p=0.002) and TP (p=0.005).

Conclusions

Autonomic nervous system does not share the leading role in premenopausal women metabolic profile. The differences in HRV between MHO and MUO women depend on the metabolic health criteria. Systolic blood pressure, HOMA and waist circumference have significant effect on HRV differences between MHO and MUO premenopausal women.

Autonomic control of cardiovascular system in pre- and postmenopausal women: a cross-sectional study

OBJECTIVE

The aim of this cross-sectional study was to assess the features of autonomic control of the cardiovascular system in pre- and postmenopausal women.

MATERIAL AND METHODS

We studied 185 postmenopausal women aged 59.3±8.5 years (mean±SD) and 104 premenopausal women aged 45.1±5.8 years. Standard indices of heart rate variability (HRV) (mean heart rate, coefficient of variation, standard deviation of the NN interval (the time elapsing between two consecutive R waves in the electrocardiogram with normal sinus rhythm) (SDNN), square root of the mean squared differences of successive NN intervals (RMSSD), proportion derived by dividing RR50, the number of interval differences of successive NN intervals greater than 50 ms, by the total number of NN intervals (PNN50), and power of low frequency (LF) and high frequency (HF) bands in absolute values and percentages of total spectral power) and index S of synchronization between the 0.1-Hz rhythms in heart rate and photoplethysmogram were compared between these two groups at rest. We assessed the following sex hormones: estradiol, follicle stimulating hormone, dehydroepiandrosterone sulfate, and testosterone.

RESULTS

Mean heart rate and power of LF and HF bands were significantly different (p<0.05) in pre- and postmenopausal women. The autonomic indices were similar in women with natural and surgical menopause. Some indices (coefficient of variation, SDNN, RMSSD, PNN50, and power of LF and HF bands) showed weak correlation with menopause time in women with natural menopause. In women with surgical menopause, a moderate statistically significant correlation was observed only between menopause time and S index (r=-0.41, p=0.039). In premenopausal women, only testosterone correlated weakly with coefficient of variation, SDNN, PNN50, RMSSD, and power of HF band. In postmenopausal women, no correlations were found. We did not find any significant relationship between autonomic indices and hot flashes, assessed by hot flash diary.

CONCLUSION

We did not find a clinically important relationship between cardiovascular autonomic control and menopausal status in women.

Brief assessment of supine heart rate variability in normal weight, overweight, and obese females

BACKGROUND

Little research has been conducted on the heart rate variability (HRV) parameters in late adolescent females. The present study aimed to assess HRV time and frequency domain parameters in overweight and obese late adolescent females. Also to assess any possible correlation between HRV parameters and obesity indices in that particular age group.

SUBJECTS AND METHODS

Fifteen-minute period of standardized ECG recording was implemented to record HRV time and frequency parameters in 42 normotensive euglycemic female medical students aged (18-21 years); lean (n = 13), overweight (n = 13), and obese (n = 16). For the analysis of results, 2.5-minute data were used.

RESULTS

Root mean squares of successive differences between adjacent RR intervals (rMSSD) and high-frequency (HF) power were significantly decreased in overweight and obese late adolescent females. Parameters reflecting sympathetic activity which include low-frequency (LF) power and LF/HF ratio showed significant increase in overweight group. Interestingly, LF power was significantly reduced in obese group while the LF/HF ratio was insignificantly different. No significant correlations were observed between HRV indices and parameters of total or visceral obesity in the study groups.

CONCLUSION

HRV indices showed sympathetic hyperactivity in overweight late adolescent females and diminished sympathetic response in matching obese group. Both overweight and obese females showed decreased protective vagal influence on the heart.

A metabolically healthy obese phenotype in hispanic participants in the IRAS family study

OBJECTIVE

Some obese individuals appear to be protected from developing type 2 diabetes mellitus and cardiovascular disease (CVD). This has led to characterizing body size phenotypes based on cardiometabolic risk factors specifically as obese or overweight, and as metabolically healthy (MH) or metabolically abnormal (MA) based upon blood pressure, lipids, glucose homeostasis, and inflammatory parameters. The aim of this study was to measure the prevalence of and describe fat distribution across these phenotypes in a minority population.

DESIGN AND METHODS

Hispanic participants (N = 1054) in the IRAS Family Study were categorized into different body size phenotypes. Computed tomography (CT) abdominal scans were evaluated for measures of nonalcoholic fatty liver disease (NAFLD) and abdominal fat distribution. Statistical models adjusting for familial relationships were estimated.

RESULTS

Seventy percent (70%) of the Hispanic cohort was overweight (32%) or obese (38%). Forty-one percent (n = 138) of overweight participants and 19% (n = 74) of obese participants met criteria for MH. Adjusted analyses showed the MH phenotype was associated with lower visceral adipose tissue (VAT) and higher liver density (indicating lower fat content) in obese participants (p = 0.0005 and p = 0.0002, respectively), and lower VAT but not liver density in overweight participants (p = 0.008 and p = 0.162, respectively) compared to their MA counterparts. Odds of NAFLD were reduced in MH obese (OR = 0.34, p = 0.0007) compared to MA obese. VAT did not differ between MH obese or overweight and normal weight groups.

CONCLUSIONS

These findings suggest that lower levels of visceral and liver fat, despite overall increased total body fat, may be a defining feature of MH obesity in Hispanic Americans.

A weight loss diet intervention has a similar beneficial effect on both metabolically abnormal obese and metabolically healthy but obese premenopausal women

BACKGROUND/AIMS

We studied the effect of a 12-week energy-restricted diet intervention on cardiometabolic risk in two groups of nonmorbid obese premenopausal Caucasian women, i.e. a metabolically abnormal obese (MAO) and a metabolically healthy but obese (MHO) group.

METHODS

The participants were 53 MAO and 25 MHO women (age range 19-49 years; body mass index inclusion criterion: 30-39.9). We assessed changes in body weight and composition, blood lipids, insulin resistance, hepatic enzymes, inflammatory markers and adipocytokines.

RESULTS

Overall, many of the study outcomes improved with the intervention in both MAO and MHO participants, but there was no difference in the magnitude of change between the groups. Body weight, waist circumference and total fat mass decreased significantly in response to the intervention in both MAO and MHO women (all p < 0.001). Fasting insulin, insulin resistance (homeostasis model assessment), hepatic enzymes (alanine aminotransferase and γ-glutamyltransferase), fatty liver index and leptin levels also decreased in both groups after the intervention (all p < 0.001), whereas total cholesterol, triglycerides and C-reactive protein decreased significantly only in MAO women (all p < 0.001).

CONCLUSION

These findings reinforce the idea that MHO women would also benefit from a lifestyle weight reduction intervention.

Are there still healthy obese patients?

PURPOSE OF REVIEW

Obesity is associated with an increased risk of premature death and represents a fast growing worldwide health problem that is reaching epidemic proportions. Obesity significantly increases the risk of developing metabolic disorders, hypertension, coronary heart disease, stroke, and several types of cancer. However, a subgroup of 'healthy' obese patients seems to be protected against metabolic and cardiovascular obesity comorbidities. This review focuses on potential mechanisms underlying the healthy obese subphenotype.

RECENT FINDINGS

Individuals with obesity typically develop type 2 diabetes, dyslipidemia, fatty liver disease, gout, hypertension, and cardiovascular disease. In the past years it became clear that up to 30% of obese patients are metabolically healthy with insulin sensitivity similar to healthy lean individuals, lower liver fat content, and lower intima media thickness of the carotid artery than the majority of metabolically 'unhealthy' obese patients. Recent studies suggest that protection against development of hepatic steatosis, ectopic fat deposition, inflammation of visceral adipose tissue, and adipose tissue dysfunction contributes to healthy obesity.

SUMMARY

For the stratification of obesity treatment, definition of metabolically healthy or high-risk phenotypes will facilitate the identification of the obese person who will benefit the most from early lifestyle, bariatric surgery, or pharmacological interventions.

The Relationship among Pulse Wave Velocity, Ankle-Brachial Pressure Index and Heart Rate Variability in Adult Males

Background

Pulse wave velocity (PWV) and ankle-brachial pressure index (ABI) are non-invasive tools to measure atherosclerosis and arterial stiffness. Heart rate variability (HRV) has proven to be a non-invasive powerful tool in the investigation of the autonomic cardiovascular control. Therefore, the purpose of this study was to determine the relationship among PWV, ABI, and HRV parameters in adult males.

Methods

The study was carried out with 117 males who visited a health care center from April, 2009 to May, 2010. We conducted blood sampling (total cholesterol, triglyceride, high density lipoprotein, cholesterol, fasting glucose) and physical examination. We studied brachial-ankle PWV (baPWV) and ABI. We examined HRV parameters including standard deviation of NN interval (SDNN), low frequency (LF), high frequency (HF), LF/HF ratio. We analyzed the relationship among baPWV, ABI, and HRV parameters.

Results

SDNN had a significant negative correlation with age, systolic blood pressure and heart rate. LF and HF had a significant negative correlation with age, and age and heart rate, respectively. baPWV was significantly and positively associated with age, systolic and diastolic blood pressures, total cholesterol, fasting glucose and heart rate. ABI was negative correlated significantly with systolic and diastolic blood pressures and heart rate. After adjusting for all associated variables, baPWV was not correlated with HRV parameters, but there was a significant positive association between SDNN and ABI (r = 0.195, P = 0.014).

Conclusion

SDNN of HRV parameters had a significant positive correlation with ABI.

All-cause mortality risk of metabolically healthy obese individuals in NHANES III

Mortality risk across metabolic health-by-BMI categories in NHANES-III was examined. Metabolic health was defined as: (1) homeostasis model assessment-insulin resistance (HOMA-IR) <2.5; (2) ≤2 Adult Treatment Panel (ATP) III metabolic syndrome criteria; (3) combined definition using ≤1 of the following: HOMA-IR ≥1.95 (or diabetes medications), triglycerides ≥1.7 mmol/L, HDL-C <1.04 mmol/L (males) or <1.30 mmol/L (females), LDL-C ≥2.6 mmol/L, and total cholesterol ≥5.2 mmol/L (or cholesterol-lowering medications). Hazard ratios (HR) for all-cause mortality were estimated with Cox regression models. Nonpregnant women and men were included (n = 4373, mean ± SD, age 37.1 ± 10.9 years, BMI 27.3 ± 5.8 kg/m², 49.4% female). Only 40 of 1160 obese individuals were identified as MHO by all definitions. MHO groups had superior levels of clinical risk factors compared to unhealthy individuals but inferior levels compared to healthy lean groups. There was increased risk of all-cause mortality in metabolically unhealthy obese participants regardless of definition (HOMA-IR HR 2.07 (CI 1.3-3.4), P < 0.01; ATP-III HR 1.98 (CI 1.4-2.9), P < 0.001; combined definition HR 2.19 (CI 1.3-3.8), P < 0.01). MHO participants were not significantly different from healthy lean individuals by any definition. While MHO individuals are not at significantly increased risk of all-cause mortality, their clinical risk profile is worse than that of metabolically healthy lean individuals.