Dual effects of insulin resistance on mortality and function in non-diabetic older adults: findings from the Toledo Study of Healthy Aging

Timing of Moderate to Vigorous Physical Activity, Mortality, Cardiovascular Disease, and Microvascular Disease in Adults With Obesity

OBJECTIVE

To assess the association between timing of aerobic moderate to vigorous physical activity (MVPA) and risk of cardiovascular disease (CVD), microvascular disease (MVD), and all-cause mortality in adults with obesity and a subset with obesity and type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Participants included adults with obesity (BMI ≥30 kg/m2) and a subset of those with T2D from the UK Biobank accelerometry substudy. Aerobic MVPA was defined as bouts of MVPA lasting ≥3 continuous minutes. Participants were categorized into morning, afternoon, or evening MVPA based on when they undertook the majority of their aerobic MVPA. The reference group included participants with an average of less than one aerobic MVPA bout per day. Analyses were adjusted for established and potential confounders.

RESULTS

The core sample included 29,836 adults with obesity, with a mean age of 62.2 (SD 7.7) years. Over a mean follow-up period of 7.9 (SD 0.8) years, 1,425 deaths, 3,980 CVD events, and 2,162 MVD events occurred. Compared with activity in the reference group, evening MVPA was associated with the lowest risk of mortality (hazard ratio [HR] 0.39; 95% CI 0.27, 0.55), whereas afternoon (HR 0.60; 95% CI 0.51, 0.71) and morning MVPA (HR 0.67; 95% CI 0.56, 0.79) demonstrated significant but weaker associations. Similar patterns were observed for CVD and MVD incidence, with evening MVPA associated with the lowest risk of CVD (HR 0.64; 95% CI 0.54, 0.75) and MVD (HR 0.76; 95% CI 0.63, 0.92). Findings were similar in the T2D subset (n = 2,995).

CONCLUSIONS

Aerobic MVPA bouts undertaken in the evening were associated with the lowest risk of mortality, CVD, and MVD. Timing of physical activity may play a role in the future of obesity and T2D management.

Biomarkers of frailty

Several biomarkers have been proposed to identify frailty, a multisystemic age-related syndrome. However, the complex pathophysiology and the absence of a consensus on a comprehensive and universal definition make it challenging to pinpoint a singular biomarker or set of biomarkers that conclusively characterize frailty. This review delves into the main laboratory biomarkers, placing special emphasis on those associated with various pathways closely tied to the frailty condition, such as inflammation, oxidative stress, mitochondrial dysfunction, metabolic and endocrine alterations and microRNA. Additionally, we provide a summary of different clinical biomarkers encompassing different tools that have been proposed to assess frailty. We further address various imaging biomarkers such as Dual Energy X-ray Absorptiometry, Bioelectrical Impedance analysis, Computed Tomography and Magnetic Resonance Imaging, Ultrasound and D3 Creatine dilution. Intervention to treat frailty, including non-pharmacological ones, especially those involving physical exercise and nutrition, and pharmacological interventions, that include those targeting specific mechanisms such as myostatin inhibitors, insulin sensitizer metformin and with special relevance for hormonal treatments are mentioned. We further address the levels of different biomarkers in monitoring the potential positive effects of some of these interventions. Despite the availability of numerous biomarkers, their performance and usefulness in the clinical arena are far from being satisfactory. Considering the multicausality of frailty, there is an increasing need to assess the role of sets of biomarkers and the combination between laboratory, clinical and image biomarkers, in terms of sensitivity, specificity and predictive values for the diagnosis and prognosis of the different outcomes of frailty to improve detection and monitoring of older people with frailty or at risk of developing it, being this a need in the everyday clinical practice.

Relationship of endogenous plasma concentrations of β-hydroxy β-methyl butyrate (HMB) with frailty in community dwelling older adults with type-2 diabetes mellitus

BACKGROUND

Supplementation with β-hydroxy β-methyl butyrate (HMB) appears to be effective in preserving muscle in older adults. However, the association between endogenously produced HMB with frailty has not been studied in people with chronic disease.

OBJECTIVES

The purpose of this study is to explore whether an association exists between endogenous HMB levels and frailty status in older adults with type-2 diabetes mellitus (T2DM).

METHODS

Data were taken from the Toledo Study of Healthy Ageing, a community-dwelling aged (65 years+) cohort. Frailty was assessed at baseline and at 2.99 median years according to the Frailty Phenotype (FP) standardized to our population and the Frailty Trait Scale 12 (FTS12). The associations between HMB levels and frailty were assessed using three nested multivariate logistic regressions and segmented by sex. Glucose, HMB and glucose interaction, age and body composition were used as covariables.

RESULTS

255 participants (mean age 75.3 years, 52.94% men) were included. HMB levels showed an inverse cross-sectional association with frailty, which was modified when the interaction term HMB*glucose was included, remaining significant only for FTS12 [OR (95% CI): 0.436 (0.253, 0.751), p-value 0.003]. The association between HMB endogenous levels and FTS12 appears to be independent of sex, in which the association was maintained after adjusting for the covariates. However, there appears to be threshold points for glucose levels, above which the protective effect of HMB is lost: 145.4 mg/dl adjusted by gender for the whole sample and 149.6 mg/dl and 138.9 mg/dl for men and women, respectively. Endogenous HMB levels were not found to be associated with incident frailty.

CONCLUSIONS

Cross-sectional analysis revealed that endogenous HMB levels were inversely associated with frailty as assessed by the FTS12 in older people with T2DM. This association was found to be dependent on circulating fasted glucose levels.

Insulin resistance drives cognitive impairment in hypertensive pre-diabetic frail elders: the CENTENNIAL study

AIMS

Pre-diabetes is a condition that confers an increased cardiovascular risk. Frailty is very common in hypertensive patients, and insulin resistance has been linked to frailty in older adults with diabetes. On these grounds, our aim was to evaluate the association between insulin resistance and cognitive impairment in hypertensive and pre-diabetic and frail older adults.

METHODS AND RESULTS

We studied consecutive pre-diabetic and hypertensive elders with frailty presenting at the Avellino local health authority of the Italian Ministry of Health (ASL AV) from March 2021 to March 2022. All of them fulfilled the following inclusion criteria: a previous diagnosis of hypertension with no clinical or laboratory evidence of secondary causes, a confirmed diagnosis of pre-diabetes, age >65 years, Montreal Cognitive Assessment (MoCA) Score <26, and frailty. We enrolled 178 frail patients, of which 141 successfully completed the study. We observed a strong inverse correlation (r = -0.807; P < 0.001) between MoCA Score and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). The results were confirmed by a linear regression analysis using MoCA Score as dependent variable, after adjusting for several potential confounders.

CONCLUSION

Taken together, our data highlight for the first time the association between insulin resistance and global cognitive function in frail elders with hypertension and pre-diabetes.

Association between metabolic syndrome and risk of both prevalent and incident frailty in older adults: Findings from The Irish Longitudinal Study on Ageing (TILDA)

OBJECTIVES

Metabolic syndrome (MetS) is a risk factor for cardiovascular disease, diabetes, and all-cause mortality. Frailty is a condition of decreased multi-system physiological reserve where one has increased vulnerability to stressors. This study aimed to examine if MetS is associated with prevalent and incident frailty over a 4-year follow-up period in an aged population.

METHODS

This study used data from waves 1 (2009-2011) and 3 (2014-2015) of The Irish Longitudinal Study on Ageing. Those aged <50 years or without baseline health assessment data were excluded. Baseline MetS status was determined using the National Cholesterol Education Program Third Adult Treatment Panel criteria. Frailty status was identified at both waves, operationalised using Fried's frailty phenotype (FP) and Rockwood's frailty index (FI). Ordinal logistic regression examined the cross-sectional association between MetS and prevalent frailty status. Those with prevalent pre-frailty or frailty were excluded and ordinal logistic regression models examined the association between MetS and incident frailty. Lastly, MetS' longitudinal associations with the five individual components of Fried's FP were examined. Models were adjusted for age, sex, education, smoking, chronic disease history and renal function.

RESULTS

Ordinal logistic regression models (n > 5100), showed MetS was associated with prevalent frailty as assessed by both FP (odds ratio (OR) 1.29, p < 0.001) and FI (OR 1.65, p < 0.001). Of those who were non-frail at baseline, 2247 participants had longitudinal FP data, while 3546 participants had longitudinal FI data. Models demonstrated that MetS was associated with an increased likelihood of incident frailty for both FP (OR 1.57, p < 0.001) and FI (OR 1.29, p = 0.014). MetS was found to be associated with incident low physical activity (OR 1.57, p = 0.001) and incident unintentional weight loss (OR 1.59, p = 0.025).

CONCLUSIONS

MetS in those ≥50 years was found to be associated with an increased likelihood of incident frailty over a 4-year period, by 57 % when measured by FP and 29 % by FI. MetS should be considered a risk factor for frailty and be taken into considered in any comprehensive geriatric assessment given frailty's dynamic nature and MetS being potentially modifiable.

Effect of dietary protein content shift on aging in elderly rats by comprehensive quantitative score and metabolomics analysis

In the protein nutrition strategy of middle-aged and elderly people, some believe that low protein is good for health, while others believe high protein is good for health. Facing the contradictory situation, the following hypothesis is proposed. There is a process of change from lower to higher ratio of protein nutritional requirements that are good for health in the human body after about 50 years of age, and the age at which the switch occurs is around 65 years of age. Hence, in this study, 50, 25-month-old male rats were randomly divided into five groups: Control (basal diet), LP (low-protein diet with a 30% decrease in protein content compared to the basal diet), HP (high-protein diet with a 30% increase in protein content compared to the basal diet), Model 1 (switched from LP to HP feed at week 4), and Model 2 (switched from LP to HP feed at week 7). After a total of 10 weeks intervention, the liver and serum samples were examined for aging-related indicators, and a newly comprehensive quantitative score was generated using principal component analysis (PCA). The effects of the five protein nutritional modalities were quantified in descending order: Model 1 &gt; HP &gt; LP &gt; Control &gt; Model 2. Furthermore, the differential metabolites in serum and feces were determined by orthogonal partial least squares discriminant analysis, and 15 differential metabolites, significantly associated with protein intake, were identified by Spearman’s correlation analysis (p &lt; 0.05). Among the fecal metabolites, 10 were positively correlated and 3 were negatively correlated. In the serum, tyrosine and lactate levels were positively correlated, and acetate levels were negatively correlated. MetaboAnalyst analysis identified that the metabolic pathways influenced by protein intake were mainly related to amino acid and carbohydrate metabolism. The results of metabolomic analysis elucidate the mechanisms underlying the preceding effects to some degree. These efforts not only contribute to a unified protein nutrition strategy but also positively impact the building of a wiser approach to protein nutrition, thereby helping middle-aged and older populations achieve healthy aging.

Effect of Physical Activity/Exercise on Oxidative Stress and Inflammation in Muscle and Vascular Aging

Functional status is considered the main determinant of healthy aging. Impairment in skeletal muscle and the cardiovascular system, two interrelated systems, results in compromised functional status in aging. Increased oxidative stress and inflammation in older subjects constitute the background for skeletal muscle and cardiovascular system alterations. Aged skeletal muscle mass and strength impairment is related to anabolic resistance, mitochondrial dysfunction, increased oxidative stress and inflammation as well as a reduced antioxidant response and myokine profile. Arterial stiffness and endothelial function stand out as the main cardiovascular alterations related to aging, where increased systemic and vascular oxidative stress and inflammation play a key role. Physical activity and exercise training arise as modifiable determinants of functional outcomes in older persons. Exercise enhances antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscle. Additionally, exercise improves endothelial function and arterial stiffness by reducing inflammatory and oxidative damage signaling in vascular tissue together with an increase in antioxidant enzymes and nitric oxide availability, globally promoting functional performance and healthy aging. This review focuses on the role of oxidative stress and inflammation in aged musculoskeletal and vascular systems and how physical activity/exercise influences functional status in the elderly.

Association between Relative Handgrip Strength and Insulin Resistance in Korean Elderly Men without Diabetes: Findings of the 2015 Korea National Health Nutrition Examination Survey

BACKGROUND

Evidence regarding the association between handgrip strength (HGS) and insulin resistance in a non-diabetic population is scarce. This study aimed to investigate the association between relative HGS and insulin resistance in older men without diabetes, using a representative sample of the Korean male population.

METHODS

The study population comprised 206 participants aged 65-80 years, selected from the 2015 Korea National Health and Nutrition Examination Survey. Insulin resistance was defined as the upper tertile of the homeostatic model assessment of insulin resistance (HOMA-IR). Odds ratios and 95% confidence intervals for insulin resistance were assessed using multiple logistic regression analyses after adjusting for confounding variables.

RESULTS

The prevalence of insulin resistance decreased with increasing relative HGS. The prevalence in the T1, T2, and T3 groups was 46.0%, 32.2%, and 26.4%, respectively. Compared with the individuals in the highest tertile of relative HGS, the odds ratio (95% confidence interval) for insulin resistance in individuals in the lowest quartile was 2.82 (1.10-7.21) after adjusting for age, smoking, alcohol consumption, aerobic exercise, resistance exercise, systolic blood pressure, total cholesterol, residential area, household income, and education level.

CONCLUSION

Lower relative HGS was inversely associated with an increased risk of insulin resistance in older Korean men without diabetes. In clinical practice, relative HGS, which is a simple and inexpensive tool, could be a useful measure for identifying older men with insulin resistance. Moreover, these findings suggest that muscle strengthening exercises should be considered to reduce insulin resistance and increase insulin sensitivity.

Biomarkers shared by frailty and sarcopenia in older adults: A systematic review and meta-analysis

BACKGROUND

Physical frailty and sarcopenia show extensive clinical similarities. Whether biomarkers exist that are shared by the two conditions is presently unclear.

METHODS

We conducted a systematic review and meta-analysis of cross-sectional and longitudinal studies that investigated the association of frailty and/or sarcopenia with biomarkers as a primary or secondary outcome in adults aged 60 years and older. Only studies published in English that defined frailty using a validated scale and/or questionnaire and diagnosed sarcopenia according to the presence of muscle atrophy plus dynapenia or low physical function were included. Studies were identified from a systematic search of MEDLINE and SCOPUS databases from inception through August 2020. The quality of reporting of each study was assessed by using the Quality Assessment Tool for Observational Cohort, Cross-Sectional and Case-Control studies of the National Institute of Health. A meta-analysis was conducted when at least three studies investigated the same biomarker in both frailty and sarcopenia. Pooled effect size was calculated based on standard mean differences and random-effect models. Sensitivity analysis was performed based on age and the setting where the study was conducted.

RESULTS

Eighty studies (58 on frailty and 22 on sarcopenia) met the inclusion criteria and were included in the qualitative analysis. Studies on frailty included 33,160 community-dwellers, hospitalized, or institutionalized older adults (60-88 years) from 21 countries. Studies on sarcopenia involved 4904 community-living and institutionalized older adults (68-87.6 years) from 9 countries. Several metabolic, inflammatory, and hematologic markers were found to be shared between the two conditions. Albumin and hemoglobin were negatively associated with both frailty and sarcopenia. Interleukin 6 was associated with frailty and sarcopenia only in people aged < 75. Community-dwelling older adults with frailty and sarcopenia had higher levels of tumor necrosis factor alpha compared with their robust and non-sarcopenic counterparts.

CONCLUSIONS

A set of metabolic, hematologic, and inflammatory biomarkers was found to be shared by frailty and sarcopenia. These findings fill a knowledge gap in the quest of biomarkers for these conditions and provide a rationale for biomarker selection in studies on frailty and sarcopenia.

Gut microbial DNA and immune checkpoint gene Vsig4/CRIg are key antagonistic players in healthy aging and age-associated development of hypertension and diabetes

AIMS

Aging is associated with the development of insulin resistance and hypertension which may stem from inflammation induced by accumulation of toxic bacterial DNA crossing the gut barrier. The aim of this study was to identify factors counter-regulating these processes. Taking advantage of the Chromogranin A (CgA) knockout (CgA-KO) mouse as a model for healthy aging, we have identified Vsig4 (V-set and immunoglobulin domain containing 4) as the critical checkpoint gene in offsetting age-associated hypertension and diabetes.

METHODS AND RESULTS

The CgA-KO mice display two opposite aging phenotypes: hypertension but heightened insulin sensitivity at young age, whereas the blood pressure normalizes at older age and insulin sensitivity further improves. In comparison, aging WT mice gradually lost glucose tolerance and insulin sensitivity and developed hypertension. The gut barrier, compromised in aging WT mice, was preserved in CgA KO mice leading to major 35-fold protection against bacterial DNA-induced inflammation. Similarly, RNA sequencing showed increased expression of the Vsig4 gene (which removes bacterial DNA) in the liver of 2-yr-old CgA-KO mice, which may account for the very low accumulation of microbial DNA in the heart. The reversal of hypertension in aging CgA-KO mice likely stems from (i) low accumulation of microbial DNA, (ii) decreased spillover of norepinephrine in the heart and kidneys, and (iii) reduced inflammation.

CONCLUSION

We conclude that healthy aging relies on protection from bacterial DNA and the consequent low inflammation afforded by CgA-KO. Vsig4 also plays a crucial role in "healthy aging" by counteracting age-associated insulin resistance and hypertension.