Concurrent reductions in blood pressure and metabolic rate during fasting in the unrestrained SHR

Abstract

Fasting produces multiple cardiovascular, metabolic, and behavioral responses. To examine the interrelationship between these responses, male spontaneously hypertensive rats (SHR; n = 8) implanted with cardiovascular telemetry devices were housed in metabolic chambers at 23 degrees C for 22-h daily measurements of physiological variables. The experimental apparatus was designed so that ingestive behavior was detected by photobeams and locomotion was detected by a load sensor. Cardiovascular and metabolic status were determined as both a function of the circadian cycle (12-h dark and 10-h light), as well as during periods of inactivity (no ingestion and minimal locomotion) within the dark and light phases. Data were obtained during baseline, 48-h of caloric deprivation, and 6 days of refeeding. Fasting produced significant reductions in mean arterial pressure (dark: -9.2+/-1.3 from 143.7+/-3.7 mm Hg; light: -8.6+/-1.8 from 140.1+/-3.7 mm Hg), heart rate (dark: -43.4+/-5.2 from 330.0+/-5.2 beats/min; light: -27.4+/-5.2 from 294.0+/-5.2 beats/min), and oxygen consumption (dark: -5.0+/-0.6 from 20.6+/-0.3 ml x min(-1) x kg (0.75); light: -2.7+/-0.2 from 14.9 +/-0.2 ml x min(-1) x kg(0.75)). Analysis of inactive periods during both light and dark phases revealed that these reductions were not dependent on behavioral effects. We conclude that fasting produces concurrent and interrelated reductions in cardiovascular and metabolic function in the SHR. The merging of cardiovascular telemetry, indirect calorimetry, and behavioral monitoring provides a powerful approach for investigation of the integrative physiological responses to energetic challenges.

Role of the arcuate nucleus of the hypothalamus in regulation of body weight during energy deficit

“…Studies on the effects of 48-72-h fasting on physical activity in rodents have given conflicting results, indicating increased (Overton et al, 2001), decreased (Williams et al, 2000) or no change in physical activity (Nagashima et al, 2003). During long-term chronic food restriction in rodents however, an increase in physical activity is generally observed.…”

Combined amylin–leptin treatment lowers blood pressure and adiposity in lean and obese rats

“…20 After surgery, animals were given subcutaneous injections of 30 mg kg -1 buprinex analgesic (Henry Schein Inc., Melville, NY, USA) and intramuscular injections of 60 mg kg -1 of cefazolin (Henry Schein Inc.) as a prophylactic.…”

“…The remaining 41 FBNF1 rats were maintained on standard chow and prepared for study shortly after reaching a stable body weight above 300-350 g. The apparatus and procedures used for determination of energy expenditure and locomotor activity have been described previously. 19,20 Briefly, rats were housed in individual polycarbonate 20 l cages each fitted for open circuit respirometry. Oxygen consumption and carbon dioxide production were continuously measured 23 h day -1 .…”

Correlation of obesity indicies and blood pressure among non obese adults in Zaria, Northern Nigeria

“…It is also a very prominent feature of the metabolic syndrome (MetS). Insulin resistance and central obesity, recognized as the main factors involved in the pathophysiology of the MetS, contribute to elevated blood pressure, which further promotes vascular damage in cardiac, renal and brain tissue (Sowers et al, 2004;Wang and Hoy, 2004 Several epidemiological studies from different populations have reported significant association between different anthropometric indicators (such as waist circumference, body mass index (BMI) and waistheight ratio) and blood pressure levels (Williams et al, 2000;Duvnjak et al, 2008;Kjeldsen et al, 2008). These associations between body fatness using different indices have been consistently observed but remain poorly understood and the mechanistic explanations for the phenomenon are still being debated and no biological model of the process has been established (Rufus et al, 2008).…”