Lessons from Toxicology: Developing a 21st-Century Paradigm for Medical Research

Biomedical developments in the 21st century provide an unprecedented opportunity to gain a dynamic systems-level and human-specific understanding of the causes and pathophysiologies of disease. This understanding is a vital need, in view of continuing failures in health research, drug discovery, and clinical translation. The full potential of advanced approaches may not be achieved within a 20th-century conceptual framework dominated by animal models. Novel technologies are being integrated into environmental health research and are also applicable to disease research, but these advances need a new medical research and drug discovery paradigm to gain maximal benefits. We suggest a new conceptual framework that repurposes the 21st-century transition underway in toxicology. Human disease should be conceived as resulting from integrated extrinsic and intrinsic causes, with research focused on modern human-specific models to understand disease pathways at multiple biological levels that are analogous to adverse outcome pathways in toxicology. Systems biology tools should be used to integrate and interpret data about disease causation and pathophysiology. Such an approach promises progress in overcoming the current roadblocks to understanding human disease and successful drug discovery and translation. A discourse should begin now to identify and consider the many challenges and questions that need to be solved.

A vision becoming reality

Non-animal science in toxicology and health research has been progressing for decades, but only now is it being seen widely as advanced science. The emergence of novel human biology-based tools and models, combined with legislative and regulatory change, a 21st century concept for toxicology, continuing failures in the drug pipeline, and systematic critiques of animal models, have created a pivotal moment of change. The leading edge is starting to become the norm. Humans and other animals are likely to benefit as a result.

Estimates for worldwide laboratory animal use in 2005

Animal experimentation continues to generate public and political concern worldwide. Relatively few countries collate and publish animal use statistics, yet this is a first and essential step toward public accountability and an informed debate, as well as being important for effective policy-making and regulation. The implementation of the Three Rs (replacement, reduction and refinement of animal experiments) should be expected to result in a decline in animal use, but without regular, accurate statistics, this cannot be monitored. Recent estimates of worldwide annual laboratory animal use are imprecise and unsubstantiated, ranging from 28-100 million. We collated data for 37 countries that publish national statistics, and standardised these against the definitions of 'animals', 'purposes' and 'experiments' used in European Union Directive 86/609/EEC. We developed and applied a statistical model, based on publication rates, for a further 142 countries. This yielded our most conservative estimate of global animal use: 58.3 million animals in 179 countries. However, this figure excludes several uses and forms of animals that are included in the statistics of some countries. With the data available, albeit for only a few countries, we also produced, by extrapolation, a more comprehensive global estimate that includes animals killed for the provision of tissues, animals used to maintain genetically-modified strains, and animals bred for laboratory use but killed as surplus to requirements. For a number of reasons that are explained, this more-comprehensive figure of 115.3 million animals is still likely to be an underestimate.

Replacing animal experiments: choices, chances and challenges

Replacing animal procedures with methods such as cells and tissues in vitro, volunteer studies, physicochemical techniques and computer modelling, is driven by legislative, scientific and moral imperatives. Non-animal approaches are now considered as advanced methods that can overcome many of the limitations of animal experiments. In testing medicines and chemicals, in vitro assays have spared hundreds of thousands of animals. In contrast, academic animal use continues to rise and the concept of replacement seems less well accepted in university research. Even so, some animal procedures have been replaced in neurological, reproductive and dentistry research and progress is being made in fields such as respiratory illnesses, pain and sepsis. Systematic reviews of the transferability of animal data to the clinical setting may encourage a fresh look for novel non-animal methods and, as mainstream funding becomes available, more advances in replacement are expected.

Report of a meeting to discuss a National Centre for the Replacement of Animals in Experiments

Following the publication of their joint proposal for a National Centre for the Replacement of Animals in Experiments in 2002, the Dr Hadwen Trust and the Lord Dowding Fund organised a meeting, held on 18 November 2003 at Portcullis House, Westminster, in London, in order to discuss the concept further. A one-page summary of their proposal is attached as an appendix, and full copies are available from the Lord Dowding Fund and the Dr Hadwen Trust. The meeting aimed to discuss the need to stimulate and promote research to replace animal experiments by means of a National Centre (a coordinating body), and how this should be established and funded. Participants, numbering about 80 in total, included politicians (national and European), government officials, scientists, funding bodies and animal welfare representatives. This report is a summary of the issues raised by speakers and other participants at the meeting.

Beneficial effects of metformin in normoglycemic morbidly obese adolescents

Hyperinsulinemia and insulin resistance are common features of obesity in humans and experimental animals. It has been demonstrated that metformin, an antihyperglycemic agent, decreases hyperinsulinemia and insulin resistance leading to decreased adiposity in obese and non-insulin-dependent diabetes mellitus (NIDDM) adults. To evaluate the antiobesity effect of metformin, we conducted a randomized double-blind placebo controlled trial in 24 hyperinsulinemic nondiabetic obese adolescents (body mass index [BMI] >30 kg/m(2)). All subjects were placed on a low-calorie (1,500 kcal for women and 1,800 kcal for men) meal plan. After an initial 1-week lead-in period, 12 subjects (mean +/- SE for age and BMI, 15.6 +/- 0.4 and 41.2 +/- 1.8, respectively) received metformin (850 mg twice daily) for 8 weeks, and 12 subjects (mean +/- SE for age and BMI, 15.7 +/- 0.5 and 40.8 +/- 1.4, respectively) received placebo. Compared to the placebo group, the metformin group had greater weight loss (6.5% +/- 0.8% v 3.8 +/- 0.4%, P <.01), greater decrease in body fat (P <.001), greater increase in fat-free mass to body fat ratio (P <.005), and greater attenuation of area under the curve (AUC) insulin response to an oral glucose tolerance test (P <.001). This was associated with enhanced insulin sensitivity, as determined by the fasting plasma glucose:insulin, 2-hour glucose:insulin, and AUC glucose:AUC insulin ratios, in the metformin group compared to controls (P <.01). This corresponded to a significant reduction in plasma leptin (P <.005), cholesterol, triglycerides, and free fatty acid (FFA) levels (P <.05) only in the metformin-treated subjects. Combined metformin treatment and low-calorie diet had a significant antiobesity effect in hyperinsulinemic obese adolescents compared to a low-calorie diet alone.

Beneficial effect of diazoxide in obese hyperinsulinemic adults

Hyperinsulinemia, insulin resistance, and increased adipose tissue are hallmarks of the obesity state in both humans and experimental animals. The role of hyperinsulinemia as a possible preceding event in the development of obesity has been proposed. We previously demonstrated that administration of diazoxide (DZ), an inhibitor of insulin secretion, to obese hyperinsulinemic Zucker rats resulted in less weight gain, enhanced insulin sensitivity, and improved glucose tolerance. Assuming that hyperinsulinemia plays a major role in the development of human obesity, then its reversal should have therapeutic potential. To test this hypothesis, we conducted a randomized placebo-controlled trial in 24 hyperinsulinemic adults [body mass index (BMI) > 30 kg/m2]. All subjects were placed on a low-calorie (1260 for females and 1570 for males) Optifast (Sandoz, Minneapolis, MN) diet. After an initial 1-week lead-in period, 12 subjects (mean +/- SE for age and BMI, 31 +/- 1 and 40 +/- 2, respectively) received DZ (2 mg/kg BW.day; maximum, 200 mg/day, divided into 3 doses) for 8 weeks; and 12 subjects (mean +/- SE for age an BMI, 28 +/- 1 and 43 +/- 1, respectively) received placebo. Compared with the placebo group, DZ subjects had greater weight loss (9.5 +/- 0.69% vs. 4.6 +/- 0.61%, P < 0.001), greater decrease in body fat (P < 0.01), greater increase in fat-free mass to body fat ratio (P < 0.01), and greater attenuation of acute insulin response to glucose (P < 0.01). However, there was no significant difference in insulin sensitivity and glucose effectiveness, as determined by the insulin-modified i.v. glucose tolerance test (Bergman's minimal model) and no significant difference in glycohemoglobin values.

CONCLUSION

8 weeks treatment with DZ had a significant antiobesity effect in hyperinsulinemic obese adults without inducing hyperglycemia.

Development of a cancellous bone structural model by stereolithography for ultrasound characterisation of the calcaneus

A novel method for the development of a user-defined structural model simulating cancellous bone of the human calcaneus is described using stereolithography (SL). The digital image of a cancellous bone section was modified by skeletonisation and dilation to produce a structural model of uniform wall thickness, determined by the resolution of the stereolithography system. Six SL models were produced using the same data file. The SL models were assessed using the McCue CUBAclinical ultrasound bone densitometer. The broadband ultrasound attenuation (BUA) and velocity (VOS) values obtained were commensurate with the commercial phantom provided with the CUBAclinical system. The intra- and inter-sample variability for the six SL models were similar at 5% for BUA and 2.5% for VOS. Stereolithography offers the potential to firstly, simulate perforation and thinning of cancellous bone associated with osteoporosis, and secondly, to evaluate the dependence of ultrasonic and mechanical parameters upon cancellous bone structure.

A phantom for evaluating bone mineral density of the hand by dual-energy x-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) is a precise, widely used method for measuring bone mineral density (BMD), usually of the lumbar spine and femoral neck. Recent developments, such as a lower x-ray tube current and pixel by pixel analysis, enable smaller bones and thinner tissues volumes, as in the hand, to be measured. Measurements of hand bone mineral content (BMC) and BMD could be useful in assessing disease severity in early rheumatoid arthritis and in monitoring disease progression and response to therapeutic intervention. A phantom is required for evaluating the software, measuring long-term precision and comparing with other DXA methods. This note describes the design and evaluation of a hand phantom for use on a Lunar DPX-L dual-energy x-ray absorptiometer. The phantom consists of three sections representing the metacarpals, and proximal and distal phalanges, using aluminum and Perspex as the bone and lean tissue equivalents respectively. The BMD of the three sections is approximately 1.0, 0.6 and 0.3 g cm-2. The phantom demonstrates limitations in the potential accuracy of BMD determination at low densities using the Small Animal Software on the Lunar DPX-L. Improved recognition of low-density regions was obtained with the Lunar EXPERT with precision values of 0.9, 1.1 and 2.0% for the three sections of the phantom respectively.

Present and Future Prospects for Using Alternatives to Chimpanzees in Research

Three chimpanzee studies of hepatitis C infection were found to be duplicative of each other and of research with human volunteers. Research into taste neurophysiology also used chimpanzees, although data which are highly relevant (but less specific) can be obtained from human studies. The use of chimps to study benzene metabolism was found to be poorly planned and unjustifiable. Scientifically, chimps are not always the best “models” for humans, and their use raises insurmountable ethical concerns. Many alternatives are already available, but researchers will need to adjust their perspectives on the usefulness of different types of data.

Ondansetron reduces chemotherapy induced nausea and vomiting refractory to standard antiemetics

Ondansetron, a selective 5HT3 (serotonin) antagonist, was used in patients refractory to standard antiemetics. Seventy-five patients receiving chemotherapy without cisplatin were given ondansetron 4 mg IV and 4 mg orally immediately prior to chemotherapy, then 8 mg orally after six and 12 hours, followed by 8 mg orally eight hourly during days 2-5. Complete control of vomiting occurred in 52 patients (69%) on the first day and 45 patients (60%) on days 2-5. Sixty patients (80%) preferred ondansetron to their previous antiemetics. The efficacy of ondansetron was maintained over multiple chemotherapy cycles. Ondansetron was also given to 16 patients receiving cisplatin chemotherapy. They received 8 mg IV immediately prior to chemotherapy followed by an infusion of 1 mg/hr for 8 hr, with 8 mg orally at the end of the infusion and then 8 mg orally eight hourly during days 2-6. Some control of vomiting (less than = 5 vomits) was achieved in eight patients (50%) on the first day and in 14 patients (87%) on subsequent days. Eight patients (50%) preferred ondansetron to their previous antiemetics. Adverse events with ondansetron were frequent but mild, with constipation and headache being most common. Ondansetron is highly effective in patients refractory to standard antiemetics, especially after noncisplatin chemotherapy.

R-wave amplitude and left ventricular volume: changes with nitroglycerine and atrial pacing

The relationship between R-wave amplitude and left ventricular volume was examined using two groups of patients, undergoing diagnostic cardiac catheterisation for investigation of chest pain, who had simultaneous R-wave recording and left ventricular angiography. R-wave amplitude was measured in leads 1, 2, 3 and V4-6. Left ventricular volume was altered by nitroglycerine (n = 18) and atrial pacing (n = 13). In both groups, increase or decrease in left ventricular volume was associated with a concomitant change of R-wave amplitude. We conclude that left ventricular volume is an important determinant of surface-recorded R waves with increased amplitude reflecting increased left ventricular volume and vice versa.