Alice E. Kane

Impact of Longevity Interventions on a Validated Mouse Clinical Frailty Index

This article investigates the effect on the mouse frailty index (FI), of factors known to influence lifespan and healthspan in mice: strain (short-lived DBA/2J mice vs long-lived C57BL/6J mice), calorie restriction (CR), and resveratrol treatment. The mouse FI, based on deficit accumulation, was recently validated in C57BL/6J mice by Whitehead JC, Hildebrand BA, Sun M, et al. (A clinical frailty index in aging mice: comparisons with frailty index data in humans. J Gerontol A Biol Sci Med Sci. 2014;69:621-632) and shares many characteristics of the human FI. FI scores were measured in male and female aged (18 months) ad-libitum fed and CR DBA/2J and C57BL/6J mice, as well as male aged (24 months) C57BL/6J mice ad-libitum fed with or without resveratrol (100 mg/kg/day) in the diet for 6 months. Mean scores of two raters were used, and the raters had excellent inter-rater reliability (ICC = 0.88, 95% CI [0.80, 0.92]). Furthermore, the interventions of CR and resveratrol were associated with a significant reduction in FI scores in C57BL/6J mice, compared to age-matched controls. The short-lived DBA/2J mice also had slightly higher FI scores than the C57BL/6J mice, for the male calorie-restricted groups (DBA/2J FI = 0.16±0.03, C57BL/6J FI = 0.11±0.03, p = .01). This study uses the mouse FI developed by Whitehead JC, Hildebrand BA, Sun M, et al. (A clinical frailty index in aging mice: comparisons with frailty index data in humans. J Gerontol A Biol Sci Med Sci. 2014;69:621-632) in a different mouse colony and shows that this tool can be applied to quantify the effect of dietary and pharmaceutical interventions on frailty.

Age-Related Changes in the Hepatic Pharmacology and Toxicology of Paracetamol

Optimal pharmacotherapy is determined when the pharmacokinetics and pharmacodynamics of the drug are understood. However, the age-related changes in pharmacokinetics and pharmacodynamics, as well as the increased interindividual variation mean optimal dose selection are a challenge for prescribing in older adults. Poor understanding of how hepatic clearance and toxicity are different with age results in suboptimal dose selection, poor efficacy, and/or increased toxicity. Of particular concern is the analgesic paracetamol which has been in use for more than 50 years and is consumed by a large proportion of older adults. Paracetamol is considered to be a relatively safe drug; however, caution must be taken because of its potential for toxicity. Paracetamol-induced liver injury from accidental overdose accounts for up to 55% of cases in older adults. Better understanding of how age affects the hepatic clearance and toxicity of drugs will contribute to evidence-based prescribing for older people, leading to fewer adverse drug reactions without loss of benefit.

Adverse Geriatric Outcomes Secondary to Polypharmacy in a Mouse Model: The Influence of Aging

We aimed to develop a mouse model of polypharmacy, primarily to establish whether short-term exposure to polypharmacy causes adverse geriatric outcomes. We also investigated whether old age increased susceptibility to any adverse geriatric outcomes of polypharmacy. Young (n= 10) and old (n= 21) male C57BL/6 mice were administered control diet or polypharmacy diet containing therapeutic doses of five commonly used medicines (simvastatin, metoprolol, omeprazole, acetaminophen, and citalopram). Mice were assessed before and after the 2- to 4-week intervention. Over the intervention period, we observed no mortality and no change in food intake, body weight, or serum biochemistry in any age or treatment group. In old mice, polypharmacy caused significant declines in locomotor activity (pre minus postintervention values in control 2 ± 13 counts, polypharmacy 32 ± 7 counts,p< .05) and front paw wire holding impulse (control -2.45 ± 1.02 N s, polypharmacy +1.99 ± 1.19 N s,p< .05), loss of improvement in rotarod latency (control -59 ± 11 s, polypharmacy -1.7 ± 17 s,p< .05), and lowered blood pressure (control -0.2 ± 3 mmHg, polypharmacy 11 ± 4 mmHg,p< .05). In young mice, changes in outcomes over the intervention period did not differ between control and polypharmacy groups. This novel model of polypharmacy is feasible. Even short-term polypharmacy impairs mobility, balance, and strength in old male mice.

Acetaminophen hepatotoxicity in mice: Effect of age, frailty and exposure type.

Acetaminophen is a commonly used analgesic that can cause severe hepatotoxicity in overdose. Despite old age and frailty being associated with extensive and long-term utilization of acetaminophen and a high prevalence of adverse drug reactions, there is limited information on the risks of toxicity from acetaminophen in old age and frailty. This study aimed to assess changes in the risk and mechanisms of hepatotoxicity from acute, chronic and sub-acute acetaminophen exposure with old age and frailty in mice. Young and old male C57BL/6 mice were exposed to either acute (300 mg/kg via oral gavage), chronic (100 mg/kg/day in diet for six weeks) or sub-acute (250 mg/kg, t.i.d., for three days) acetaminophen, or saline control. Pre-dosing mice were scored for the mouse clinical frailty index, and after dosing serum and liver tissue were collected for assessment of toxicity and mechanisms. There were no differences with old age or frailty in the degree of hepatotoxicity induced by acute, chronic or subacute acetaminophen exposure as assessed by serum liver enzymes and histology. Age-related changes in the acetaminophen toxicity pathways included increased liver GSH concentrations, increased NQO1 activity and an increased pro- and anti-inflammatory response to acetaminophen in old age. Frailty-related changes included a negative correlation between frailty index and serum protein, albumin and ALP concentrations for some mouse groups. In conclusion, although there were changes in some pathways that would be expected to influence susceptibility to acetaminophen toxicity, there was no overall increase in acetaminophen hepatotoxicity with old age or frailty in mice.

Animal models of frailty: current applications in clinical research

The ethical, logistical, and biological complications of working with an older population of people inherently limits clinical studies of frailty. The recent development of animal models of frailty, and tools for assessing frailty in animal models provides an invaluable opportunity for frailty research. This review summarizes currently published animal models of frailty including the interleukin-10 knock-out mouse, the mouse frailty phenotype assessment tool, and the mouse clinical frailty index. It discusses both current and potential roles of these models in research into mechanisms of frailty, interventions to prevent/delay frailty, and the effect of frailty on outcomes. Finally, this review discusses some of the challenges and opportunities of translating research findings from animals to humans.

The impact of age and frailty on ventricular structure and function in C57BL/6J mice

Heart size increases with age (called hypertrophy), and its ability to contract declines. However, these reflect average changes that may not be present, or present to the same extent, in all older individuals. That aging happens at different rates is well accepted clinically. People who are aging rapidly are frail and frailty is measured with a ‘frailty index’. We quantified frailty with a validated mouse frailty index tool and evaluated the impacts of age and frailty on cardiac hypertrophy and contractile dysfunction. Hypertrophy increased with age, while contractions, calcium currents and calcium transients declined; these changes were graded by frailty scores. Overall health status, quantified as frailty, may promote maladaptive changes associated with cardiac aging and facilitate the development of diseases such as heart failure. To understand age‐related changes in heart structure and function, it is essential to know both chronological age and the health status of the animal.

Factors that Impact on Interrater Reliability of the Mouse Clinical Frailty Index

Dear Editor, We read with great interest the article “Reliability of a Frailty Index Based on the Clinical Assessment of Health Deficits in Male C57BL/6J Mice” recently published online in the Journal of Gerontology Biological Sciences (1). Feridooni and colleagues investigated the reliability of a recently developed mouse clinical frailty index between two raters, in three separate groups of male C57BL/6 mice aged 0.9–1.2 years, with discussion and refinement of index descriptors between assessment of each group. They found high overall inter-rater reliability, and that measures of reliability increased sequentially over the three groups. Our assessment of the mouse clinical frailty index in one published (2) and two unpublished studies of male C57BL/6 mice shed further light on factors that impact on its inter-rater reliability. Our studies clarify that practice and experience with assessment of the mouse clinical frailty index, without discussion or refinement, does not improve inter-rater reliability. We have completed two projects assessing the frailty index of old (Project 1 n = 55, 26.1±0.5 months; Project 2 n = 17, 23.9±0.2 months) mice before and after 4–6 weeks of a dietary/pharmaceutical intervention. Each project used two raters for the frailty index, who did not discuss or compare their scoring until the completion of the projects. The inter-rater reliability between the two raters for both of these projects did not improve with practice or experience (Project 1 Pre ICC=0.522[CI 0.181–0.721], p = .00; r 2 = .361, p = .00; Post ICC = 0.488[CI 0.244–0.652], p = .01; r 2 = .328, p = .00; Project 2 Pre ICC = 0.705[CI 0.186–0.893], p = .01; r 2 = .562, p = .02; Post ICC = 0.561[CI 0.122–0.781], p = .01; r 2 = .391, p = .02). These results fall within the range of reliability statistics observed by Feridooni and colleagues (1), using different raters in different research groups and countries. Another factor that we have identified as affecting the inter-rater reliability when assessing the mouse clinical frailty index is the professional background and baseline animal training of the raters. In order to explore this, we had four raters assess the clinical frailty index of a cohort of old (n = 74, 19.0±1.0 months) mice, with no discussion or training period. Two raters were animal technicians with 5–10 years of experience and training in animal handling, and two raters were research scientists with minimal animal handling training, and 3–6 years of animal research experience. Interestingly, the inter-rater reliability between the technicians and researchers was poor (ICC = 0.201–0.489, p < .05; r 2 = −0.028 to 0.33, p < .05), despite moderate inter-rater reliability between the technicians (ICC = 0.605[CI 0.344–0.762], p = .00; r 2 = .454, p = .00) and excellent inter-rater reliability between the scientists (ICC=0.88[95%CI 0.80–0.92] p = 0.00; r 2 = .817, p = .00). Furthermore, it does appear to be the background, rather than the years of experience that are important, as the inter-rater reliabilities in our pre and post intervention studies (data above), which were all performed by scientists, were moderate to high despite the raters including PhD students and a senior postdoc/laboratory manager. This suggests that the selection of raters for the mouse clinical frailty index must be done carefully, and preference given to raters with the same training/background, but not necessarily experience level, if comparisons are to be made between and across mouse groups and studies.

Development of a Rat Clinical Frailty Index

Abstract Rats are a commonly used model for aging studies, and a frailty assessment tool for rats would be of considerable value. There has been a recent focus on the development of preclinical models of frailty in mice. A mouse clinical frailty index (FI) was developed based on clinical frailty assessment tools. This FI measures the accumulation of clinically evident health-related deficits in mice. This paper aimed to develop a rat clinical FI. Male Fischer 344 rats were aged from 6 to 9 months (n = 12), and from 13 to 21 months (n = 41). A FI comprised of 27 health-related deficits was developed from a review of the literature and consultation with a veterinarian. Deficits were scored 0 if absent, 0.5 if mild, or 1 if severe. A FI score was determined for each rat every 3–4 months, and for the older group mortality was assessed up to 21 months. Mean FI scores significantly increased at each time point for the older rats. A high FI score measured at both 17 months of age and terminally was also associated with decreased probability of survival as assessed with Kaplan–Meier curves. The rat clinical FI has significant value for use in aging and interventional studies.

Characteristics of older and younger patients with suspected paracetamol toxicity

Aim:  The aim of this study was to compare the characteristics of older and younger patients with suspected paracetamol toxicity.

The effect of ageing on isoniazid pharmacokinetics and hepatotoxicity in Fischer 344 rats.

Isoniazid is the first‐line treatment for tuberculosis; however, its use is limited by hepatotoxicity. Age‐related differences in isoniazid pharmacokinetics and hepatotoxicity are uncertain. We aimed to investigate these in young (3 ± 0 months, n = 26) and old (23.0 ± 0.2 months, n = 27) male Fischer 344 rats following a low‐ or high‐dose toxic regimen of isoniazid or vehicle (4 doses/day over 2 days; low: 100, 75, 75, 75 mg/kg; high: 150, 105, 105, 105 mg/kg i.p. every 3 h). Fifteen hours after the last dose, animals were euthanized and sera and livers were prepared for analysis. Isoniazid treatment increased serum hepatotoxicity markers (alanine and aspartate transaminase) in young animals but not in old animals, and only reached significance with the high dose in young animals. Isoniazid treatment caused a trend towards an increase in necrosis in young animals with both doses. In contrast, microvesicular steatosis was increased in old isoniazid‐treated animals, reaching significance only with the low dose (steatosis prevalence in old: vehicle 1/9, isoniazid 4/5; P < 0.05). Among isoniazid‐treated animals, concentrations of toxic intermediates acetylhydrazine and hydrazine were higher in old than young animals (P < 0.05). With both doses, hepatic cytochrome P450 2E1 activity was higher in young animals compared with old (P < 0.05). There were no other age effects seen on any of the other measured enzymes involved in isoniazid metabolism (N‐acetyl transferase, amidase, glutathione‐S‐transferase). These results show age‐related changes in isoniazid pharmacokinetics may contribute towards differential patterns of toxicity and confirm that standard hepatotoxicity markers do not detect isoniazid‐induced microvesicular steatosis.