Modulation of frailty syndrome by diet: A review of evidence from mouse studies

Longitudinal fragility phenotyping contributes to the prediction of lifespan and age-associated morbidity in C57BL/6 and Diversity Outbred mice

Aging studies in mammalian models often depend on natural lifespan data as a primary outcome. Tools for lifespan prediction could accelerate these studies and reduce the need for veterinary intervention. Here, we leveraged large-scale longitudinal frailty and lifespan data on two genetically distinct mouse cohorts to evaluate noninvasive strategies to predict life expectancy in mice. We applied a modified frailty assessment, the Fragility Index, derived from existing frailty indices with additional deficits selected by veterinarians. We developed an ensemble machine learning classifier to predict imminent mortality (95% proportion of life lived [95PLL]). Our algorithm represented improvement over previous predictive criteria but fell short of the level of reliability that would be needed to make advanced prediction of lifespan and thus accelerate lifespan studies. Highly sensitive and specific frailty-based predictive endpoint criteria for aged mice remain elusive. While frailty-based prediction falls short as a surrogate for lifespan, it did demonstrate significant predictive power and as such must contain information that could be used to inform the conclusion of aging experiments. We propose a frailty-based measure of healthspan as an alternative target for aging research and demonstrate that lifespan and healthspan criteria reveal distinct aspects of aging in mice.

Longitudinal Fragility Phenotyping Predicts Lifespan and Age-Associated Morbidity in C57BL/6 and Diversity Outbred Mice

Aging studies in mammalian models often depend on natural lifespan data as a primary outcome. Tools for lifespan prediction could accelerate these studies and reduce the need for veterinary intervention. Here, we leveraged large-scale longitudinal frailty and lifespan data on two genetically distinct mouse cohorts to evaluate noninvasive strategies to predict life expectancy in mice. We applied a modified frailty assessment, the Fragility Index, derived from existing frailty indices with additional deficits selected by veterinarians. We developed an ensemble machine learning classifier to predict imminent mortality (95% proportion of life lived [95PLL]). Our algorithm represented improvement over previous predictive criteria but fell short of the level of reliability that would be needed to make advanced prediction of lifespan and thus accelerate lifespan studies. Highly sensitive and specific frailty-based predictive endpoint criteria for aged mice remain elusive. While frailty-based prediction falls short as a surrogate for lifespan, it did demonstrate significant predictive power and as such must contain information that could be used to inform the conclusion of aging experiments. We propose a frailty-based measure of healthspan as an alternative target for aging research and demonstrate that lifespan and healthspan criteria reveal distinct aspects of aging in mice.

Nutrition and dietary restrictions in cancer prevention

The composition and pattern of dietary intake have emerged as key factors influencing aging, regeneration, and consequently, healthspan and lifespan. Cancer is one of the major diseases more tightly linked with aging, and age-related mortality. Although the role of nutrition in cancer incidence is generally well established, we are far from a consensus on how diet influences tumour development in different tissues. In this review, we will discuss how diet and dietary restrictions affect cancer risk and the molecular mechanisms potentially responsible for their effects. We will cover calorie restriction, intermittent fasting, prolonged fasting, fasting-mimicking diet, time-restricted eating, ketogenic diet, high protein diet, Mediterranean diet, and the vegan and vegetarian diets.

Analysis of systolic and diastolic blood pressure variability in frail, pre-frail, and non-frail elderly patients: The relationship between frailty syndrome and blood pressure variability in the elderly

Frailty can change the prognosis and treatment approach of chronic diseases. We, therefore, conducted this study to explore the relationship between frailty syndrome and blood pressure variability in the elderly. The clinical data of 150 elderly patients with debilitating syndrome admitted to the neurology department of our hospital from May 2021 to May 2022 were selected, and they were grouped according to Fried debilitation scale and divided into 50 cases each in the debilitation group, pre-debilitation group, and no-debilitation group. The general data, co-morbidities, medications, and biochemical indexes were collected. The 24-hour ambulatory blood pressure monitoring was performed in each group, and the mean systolic blood pressure, diastolic blood pressure, nocturnal systolic load value, and diastolic load value were analyzed to determine the relationship between blood pressure variability and senile frailty. Serum albumin (ALB) and high-density lipoprotein were significantly lower in the debilitated and pre-debilitated groups than in the non-debilitated group (P < .05). Multivariate logistic regression analysis revealed that age (odds ratio [OR]: 3.910, 95% confidence intervals [CI]: 2.021-5.402) was a risk factor for frailty in the elderly, and serum ALB (OR: 0.656, 95% CI: 0.110-0.960) and HDL (OR: 0.581, 95% CI: 0.237-0.944) were protective factors for frailty in the elderly. Age, type of medication taken, co-morbidities, serum ALB, and HDL are influencing factors of debilitating syndrome. Serum ALB and HDL are protective factors against debilitating syndrome in the elderly. Age is an independent risk factor of debilitation in the elderly and increased fluctuation of blood pressure in the elderly can increase their risk of developing debilitating syndrome.

The Use of Dietary Supplements and Amino Acid Restriction Interventions to Reduce Frailty in Pre-Clinical Models

Frailty is a state of accelerated aging that increases susceptibility to adverse health outcomes. Due to its high societal and personal costs, there is growing interest in discovering beneficial interventions to attenuate frailty. Many of these interventions involve the use of lifestyle modifications such as dietary supplements. Testing these interventions in pre-clinical models can facilitate our understanding of their impact on underlying mechanisms of frailty. We conducted a narrative review of studies that investigated the impact of dietary modifications on measures of frailty or overall health in rodent models. These interventions include vitamin supplements, dietary supplements, or amino acid restriction diets. We found that vitamins, amino acid restriction diets, and dietary supplements can have beneficial effects on frailty and other measures of overall health in rodent models. Mechanistic studies show that these effects are mediated by modifying one or more mechanisms underlying frailty, in particular effects on chronic inflammation. However, many interventions do not measure frailty directly and most do not investigate effects in both sexes, which limits their applicability. Examining dietary interventions in animal models allows for detailed investigation of underlying mechanisms involved in their beneficial effects. This may lead to more successful, translatable interventions to attenuate frailty.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD⁺ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

Nutritional domains in frailty tools: Working towards an operational definition of nutritional frailty

Different methods have been proposed for the assessment of the nutritional status in frailty phenotypes. In the present narrative review article, we have summarized the number and specifications of nutritional items in existing frailty tools, in order to develop a possible means of assessment and operational definition of the nutritional frailty phenotype. In six different databases until December 2019, we searched for original articles regarding frailty tools (i.e., scales, indexes, scores, questionnaires, instruments, evaluations, screening, indicators), analyzing each tool regarding nutritional items. We identified 160 articles describing 71 frailty tools. Among the selected frailty tools, 54 were community-based (70 %), 17 hospital-based (22 %), 4 validated in long-term care institutions for older adults (LTCIOA) (5.1 %) and 2 validated in both community- and hospital-based settings, including LTCIOA (2.5 %). Fifty-two of these tools (73 %) included at least one nutritional item. Twenty-two (42 %) reported two or more nutritional items. The items were grouped in the following categories: A) anthropometric measurements, B) laboratory measurements, and C) other nutritional-related measurements. Anthropometric measurements stood out compared to all other items. Nutritional items are included in the majority of frailty tools, strengthening the concept that they may have a direct implication on an increased risk of adverse health-related outcomes in frail subjects. This supports the development of the concept of nutritional frailty as an independent frailty phenotype. Subsequent steps will be to assess the contribution of each nutritional item to a possible operational definition of nutritional frailty and define the items that may best identify this new frailty phenotype.

Contributors, risk associates, and complications of frailty in patients with chronic kidney disease: a scoping review

Frailty exhibits diverse influences on health-related outcomes and represents a surrogate of increased susceptibility to harmful injuries. Patients with chronic kidney disease (CKD) are at a higher risk of accelerated biologic aging, and, in this population, the concept of frailty emerges as an instrumental measurement of physiologic reserves. However, a comprehensive description of known independent contributors to, and risk associates of, frailty in these patients remain unavailable. In the present review, original studies up to 28 February 2019 that assessed frailty in patients with all stages of CKD were retrieved and reviewed, with results extracted and summarized. By pooling 62 original investigations, 58.1% and 49.1% used cohort and cross-sectional designs, respectively. Dialysis-dependent end-stage renal disease patients (n = 39; 62.9%) were the most commonly examined population, followed by those with nondialysis CKD (n = 12; 19.4%) and those receiving renal transplantation (n = 11; 17.7%). Contributors to frailty in CKD patients included sociodemographic factors, smoking, CKD severity, organ-specific comorbidities, depression, hypoalbuminemia, and low testosterone levels. Conversely, the development of frailty was potentially associated with the emergence of cardiometabolic, musculoskeletal, and cerebral complications; mental distress; and a higher risk of subsequent functional and quality-of-life impairment. Moreover, frailty in CKD patients increased healthcare utilization and consistently elevated mortality among affected ones. Based on the multitude of contributors to frailty and its diverse health influences, a multifaceted approach to manage CKD patients with frailty is needed, and its potential influences on outcomes besides mortality need to be considered.