Long term assessment of blood pressure transducer drift in rhesus monkeys chronically instrumented with telemetry implants

Does mean arterial blood pressure scale with body mass in mammals? Effects of measurement of blood pressure

For at least the last 30 years, it has been discussed whether mean arterial blood pressure (MAP) is independent of body mass or whether it increases in accordance with the vertical height between the heart and the brain. The debate has centred on the most appropriate mathematical models for analysing allometric scaling and phylogenetic relationships; there has been previously little focus on evaluating the validity of underlying physiological data. Currently, the 2 most comprehensive scaling analyses are based on data from 47 species of mammals, based on 114 references. We reviewed all available references to determine under which physiological conditions MAP had been recorded. In 44 (38.6%) of the cited references, MAP was measured in anaesthetized animals. Data from conscious animals were reported in 59 (51.8%) of references; of these, 3 (2.6%) were radiotelemetric studies. In 5 species, data were reported from both anaesthetized and conscious animals, and the mean difference in the MAP between these settings was 20 ± 29 mm Hg. From a literature search, we identified MAP measurements performed by radiotelemetry in 11 of the 47 species included in the meta-analyses. A Bland-Altman analysis showed a bias of 1 mm Hg with 95% confidence interval (from -35 to 36 mm Hg); that is, the limits of agreement between radiotelemetric studies and studies in restrained animals were double the supposed difference in the MAP between the mouse and elephant. In conclusion, the existing literature does not provide evidence for either a positive or neutral scaling of arterial pressure to body mass across taxa.

Use and Importance of Nonhuman Primates in Metabolic Disease Research: Current State of the Field

Obesity and its multiple metabolic sequelae, including type 2 diabetes, cardiovascular disease, and fatty liver disease, are becoming increasingly widespread in both the developed and developing world. There is an urgent need to identify new approaches for the prevention and treatment of these costly and prevalent metabolic conditions. Accomplishing this will require the use of appropriate animal models for preclinical and translational investigations in metabolic disease research. Although studies in rodent models are often useful for target/pathway identification and testing hypotheses, there are important differences in metabolic physiology between rodents and primates, and experimental findings in rodent models have often failed to be successfully translated into new, clinically useful therapeutic modalities in humans. Nonhuman primates represent a valuable and physiologically relevant model that serve as a critical translational bridge between basic studies performed in rodent models and clinical studies in humans. The purpose of this review is to evaluate the evidence, including a number of specific examples, in support of the use of nonhuman primate models in metabolic disease research, as well as some of the disadvantages and limitations involved in the use of nonhuman primates. The evidence taken as a whole indicates that nonhuman primates are and will remain an indispensable resource for evaluating the efficacy and safety of novel therapeutic strategies targeting clinically important metabolic diseases, including dyslipidemia and atherosclerosis, type 2 diabetes, hepatic steatosis, steatohepatitis, and hepatic fibrosis, and potentially the cognitive decline and dementia associated with metabolic dysfunction, prior to taking these therapies into clinical trials in humans.

Assessment of the clinical cardiac drug-drug interaction associated with the combination of hepatitis C virus nucleotide inhibitors and amiodarone in guinea pigs and rhesus monkeys

In 2015, European and U.S. health agencies issued warning letters in response to 9 reported clinical cases of severe bradycardia/bradyarrhythmia in hepatitis C virus (HCV)-infected patients treated with sofosbuvir (SOF) in combination with other direct acting antivirals (DAAs) and the antiarrhythmic drug, amiodarone (AMIO). We utilized preclinical in vivo models to better understand this cardiac effect, the potential pharmacological mechanism(s), and to identify a clinically translatable model to assess the drug-drug interaction (DDI) cardiac risk of current and future HCV inhibitors. An anesthetized guinea pig model was used to elicit a SOF+AMIO-dependent bradycardia. Detailed cardiac electrophysiological studies in this species revealed SOF+AMIO-dependent selective nodal dysfunction, with initial, larger effects on the sinoatrial node. Further studies in conscious, rhesus monkeys revealed an emergent bradycardia and bradyarrhythmia in 3 of 4 monkeys administered SOF+AMIO, effects not observed with either agent alone. Morever, bradycardia and bradyarrhythmia were not observed in rhesus monkeys when intravenous infusion of MK-3682 was completed after AMIO pretreatment.

CONCLUSIONS

These are the first preclinical in vivo experiments reported to replicate the severe clinical SOF+AMIO cardiac DDI and provide potential in vivo mechanism of action. As such, these data provide a preclinical risk assessment paradigm, including a clinically relevant nonhuman primate model, with which to better understand cardiovascular DDI risk for this therapeutic class. Furthermore, these studies suggest that not all HCV DAAs and, in particular, not all HCV nonstructural protein 5B inhibitors may exhibit this cardiac DDI with amiodarone. Given the selective in vivo cardiac electrophysiological effect, these data enable targeted cellular/molecular mechanistic studies to more precisely identify cell types, receptors, and/or ion channels responsible for the clinical DDI. (Hepatology 2016;64:1430-1441).

Vascular flow reserve as a link between long-term blood pressure level and physical performance capacity in mammals

Mean arterial pressure (MAP) is surprisingly similar across different species of mammals, and it is, in general, not known which factors determine the arterial pressure level. Mammals often have a pronounced capacity for sustained physical performance. This capacity depends on the vasculature having a flow reserve that comes into play as tissue metabolism increases. We hypothesize that microvascular properties allowing for a large vascular flow reserve is linked to the level of the arterial pressure.To study the interaction between network properties and network inlet pressure, we developed a generic and parsimonious computational model of a bifurcating microvascular network where diameter and growth of each vessel evolves in response to changes in biomechanical stresses. During a simulation, the network develops well-defined arterial and venous vessel characteristics. A change in endothelial function producing a high precapillary resistance and thus a high vascular flow reserve is associated with an increase in network inlet pressure. Assuming that network properties are independent of body mass, and that inlet pressure of the microvascular network is a proxy for arterial pressure, the study provides a conceptual explanation of why high performing animals tend to have a high MAP.