New Orleans, VA - Obesity can cause a wide range of cardiovascular disease risks, some of which can be attributed to the various differences in regional body fat distribution among individuals. For example, abdominal obesity is associated with a clustering of several cardiovascular disease risk factors and as such is an independent risk factor for cardiovascular mortality. This �clustering� of risk factors,� often referred to as �Syndrome X� or the �Metabolic Syndrome,� is more closely associated with abdominal visceral fat than obesity per se.
The Centers for Disease Control and Prevention (CDC) reported earlier this year that more than one in five Americans � an estimated 47 million persons � suffer from obesity, which greatly increases a person�s chance for heart disease, diabetes and stroke. The characterisits of the Metabolic Syndrome include a large waistline, elevated triglycerides (fats in the blood), low levels of high density lipoprotein (HDL) � commonly referred to as �good cholesterol,� high blood pressure and high blood sugar.
The cardiovagal baroreflex plays a key role in the beat-to-beat regulation of arterial blood pressure. Previous studies have suggested that cardiovagal baroreflex gain may be reduced in obese humans. Impaired cardiovagal baroreflex gain has been associated with electrical instability of the myocardium and an increased risk for cardiovascular disease-related death. Therefore, the lower cardiovagal baroreflex gain in obese individuals may have important implications for improving our understanding of the changes in cardiovascular physiology and cardiovascular disease risk that accompany obesity and the �Metabolic Syndrome.�
Previous research associated with this issue has relied on observing body mass index (BMI), or waist circumference, which are markers of total body fat and body fat distribution. Therefore, the influence of elevated abdominal fat on cardiovagal baroreflex gain remains unclear. Furthermore, there is currently no information available on the influence of elevated abdominal visceral fat on cardiovagal baroreflex gain. This represents a critical void in the existing knowledge because much of the cardiovascular disease risk associated with obesity has been attributed to elevated abdominal visceral fat.
The Study
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A new study entitled, "Cardiovagal Baroreflex Gain Reduced In Visceral Obesity," attempts to fill that void. The author is Stacy D. Beske, Ph.D, of the Harvard Medical School, Hebrew Rehabilitation Center for Aged, Research and Training Institute, Laboratory for Cardiovascular Research, Boston, MA. She will present her findings in detail at the American Physiological Society�s (APS) annual meeting, part of the "Experimental Biology 2002--Translating the Genome,� conference. More than l2,000 attendees are attending the conference which is being held April 20-24, 2002 at the Ernest N. Morial Convention Center, New Orleans, LA.
Methodology
Dr. Beske conducted her study at the Human Integrative Physiology Laboratory, Colorado State University, Fort Collins, CO. Measurements of cardiovagal baroreflex gain (modified Oxford technique), body composition (dual energy X-ray absorptiometry), and abdominal visceral and subcutaneous fat (computed tomography) were undertaken in 17 overweight and obese, sedentary men (age, 18-40 years of age; body mass index, <34.9 kg/m2).
Results
Her study revealed that:
- cardiovagal baroreflex gain was reduced in men with higher levels of total body and abdominal fat compared with their age-matched peers with lower levels; and
- cardiovagal baroreflex gain was reduced in men with elevated abdominal visceral fat compared with their age-, total body-, and abdominal subcutaneous fat-matched peers with lower levels.
Conclusions Taken together, these observations suggest that the lower cardiovagal baroreflex gain observed in overweight and obese men is linked to their higher level of abdominal visceral fat.
Excessive accumulation of body fat, or obesity, particularly in the abdominal visceral region, is an important risk factor for cardiovascular diseases. Reduced cardiovagal baroreflex gain is also associated with increased cardiovascular mortality. Therefore, reduced cardiovagal baroreflex gain may contribute to the greater risk observed in the men with characteristics of the Metabolic Syndrome. In turn, reductions in total body and abdominal visceral fat may result in improvements in cardiovascular disease risk factors.
Thus, it is possible that weight loss may improve cardiovagal baroreflex gain in men with excess total body and abdominal visceral fat and, in turn, lower their risk of cardiovascular disease.
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The American Physiological Society (APS) is one of the world�s most prestigious organizations for physiological scientists. These researchers specialize in understanding the processes and functions underlying human health and disease. Founded in 1887 the Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals each year.
Source: American Physiological Society
