Basal cell carcinoma genetic susceptibility increases the rate of skin ageing: a Mendelian randomization study.

BACKGROUND: Onset of basal cell carcinoma (BCC) is connected to skin ageing, but it is unclear whether higher BCC genetic susceptibility drives skin ageing. OBJECTIVES: To investigate whether loci increasing genetic susceptibility to BCC also drive multiple features of skin ageing, independently of confounding factors, using Mendelian randomization. METHODS: A Mendelian randomization study was conducted in older adults from the Leiden Longevity Study (N = 604). A total of 25 BCC loci, selected based on a published genome-wide association study on BCC (P-value < 5 × 10-8 ), were used as genetic instruments for the calculation of a standardized (mean = 0, SD = 1) weighted BCC genetic risk score. Based on facial photographs, we determined perceived age, and skin wrinkling and pigmented spot grading. RESULTS: A higher BCC genetic risk score was associated with a higher perceived age (adjusted for chronological age and sex) of 0.88 years (95% CI: 0.44, 1.31; P-value = 7.1e-5 ), greater wrinkling by 0.14 grades (95% CI: 0.05, 0.23; P-value = 2.3e-3 ), and greater pigmented spots by 0.17 grades (95% CI: 0.08, 0.25; P-value = 1.1e-4 ). These findings were weakened but still present after exclusion of gene variants in MC1R and IRF4 which have potential pleiotropic effects. CONCLUSIONS: Mechanisms influenced by genetic loci increasing susceptibility to BCC also drive skin ageing suggesting shared biology and shared targets for interventions.

High-sensitivity C-reactive protein, low-grade systemic inflammation and type 2 diabetes mellitus: A two-sample Mendelian randomization study.

BACKGROUND AND AIMS: The role of inflammation in type 2 diabetes mellitus (T2D) remains unclear. We investigated the associations of high sensitivity C-reactive protein (hsCRP) concentration with T2D and glycemic traits using two-sample Mendelian Randomization. METHODS AND RESULTS: We used publically available summary-statistics data from genome-wide association studies on T2D (DIAGRAM: 12 171 cases; 56 862 controls) and glycemic traits (MAGIC: 46 186 participants without diabetes mellitus). We combined the effects of the genetic instrumental variables through inverse-variance weighting (IVW), and MR-Egger regression and weighted-median estimation as sensitivity analyses which take into account potential violations (e.g., directional pleiotropy) of the assumptions of instrumental variable analyses. Analyses were conducted using 15 known hsCRP genetic instruments among which 6 instruments are hsCRP specific and not involved in inflammatory processes beyond hsCRP concentration regulation. Though we found no association between the combined effect of the genetic instrumental variables for hsCRP and T2D with IVW (odds ratio per 1 ln [hsCRP in mg/L]: 1.15; 95% confidence interval: 0.93, 1.42), we found associations for T2D with MR-Egger regression and weighted-median estimation (odds ratio with 95% confidence interval per 1 ln [hsCRP in mg/L], MR-Egger regression: 1.29; 1.08, 1.49; weighted-median estimator: 1.21; 1.02, 1.39). We found no association with T2D for the combination of hsCRP-specific genetic instruments nor did we found associations with glycemic traits in any of the analyses. CONCLUSION: Evidence was provided for a potential causal association between hsCRP and T2D, but only after considering directional pleiotropy. However, hsCRP was not causally associated with glycemic traits.

Interrelationship of the rs7903146 TCF7L2 gene variant with measures of glucose metabolism and adiposity: The NEO study.

BACKGROUND AND AIMS: We investigated the interrelationship of rs7903146-T in TCF7L2 with measures of glucose metabolism and measures of adiposity. METHODS AND RESULTS: This cross-sectional analysis was conducted in 5744 middle-aged participants (mean (standard deviation [SD]) age is 55.9 (6.0) years) from the Netherlands Epidemiology of Obesity (NEO) Study. Associations between rs7903146-T and Type 2 diabetes mellitus (T2D) were assessed with logistic regression. Additive (per-allele) associations with measures of glucose metabolism (e.g., fasting insulin) and adiposity (e.g., body mass index [BMI]) were examined with multivariable linear regression. In the total study population, rs7903146-T was associated with a higher risk of T2D (additive odds ratio: 1.42; 95% confidence interval: 1.17; 1.72), and specifically with T2D treated with insulin analogs (2.31 [1.19; 4.46]). After exclusion of participants treated with glucose-lowering medication, rs7903146-T was associated with lower mean insulin concentration (additive mean difference: -0.07 SD [-0.14; 0.00]), but not with higher mean glucose concentration (0.03 SD [-0.01; 0.07]). Furthermore, rs7903146-T was associated with, among other measures of adiposity, a lower mean BMI (-0.04 SD [-0.09; -0.00]), and a lower mean total body fat (-0.04 SD [-0.08; -0.00]). The association between rs7903146-T and T2D increased after adjustment for BMI (odds ratio: 1.51 [1.24; 1.86]); the association between rs7903146-T and fasting insulin diminished after adjustment (-0.05 SD [-0.11; 0.02]). CONCLUSION: rs7903146-T is associated with a decreased insulin concentration and increased risk of T2D with opposing effects of adjustment for adiposity.

Genetic variation in the obesity gene FTO is not associated with decreased fat oxidation: the NEO study.

BACKGROUND: The fat mass and obesity-associated (FTO) gene harbors the strongest common genetic variant associated with obesity. Recently, rs1421085-T to -C substitution mapped in FTO was shown to induce a developmental shift of human adipocytes from an energy-combusting beige to an energy-storing white phenotype in vitro. As browning of adipocytes selectively enhances fat oxidation (FatOx), we hypothesized that rs1421085-C in FTO is associated with deceased FatOx compared with carbohydrate oxidation (CarbOx) and an increased respiratory quotient (RQ). METHODS: In the Netherlands Epidemiology of Obesity study, a population-based cohort study of middle-aged individuals (45-65 years), anthropometry and genotyping was performed (n=5744), in addition to indirect calorimetry (n=1246). With linear regression analyses, we examined associations of rs1421085 genotype with FatOx, CarbOx and RQ. RESULTS: In the total study population, 36.7% carried the rs1421085-TT genotype, 47.6% rs1421085-CT and 15.7% rs1421085-CC. Mean (s.d.) age was 56 (6) years, mean (s.d.), body mass index (BMI) was 26.3 (4.4) kg m-2 and 56% of the total population were women. Measures of adiposity (difference, 95% confidence interval) were higher in CC carriers compared with that in rs1421085-TT carriers: BMI +0.56 (0.15, 0.98) kg m-2, waist circumference +1.25 (0.02, 2.49) cm and total body fat mass +1.21 (0.28, 2.14) kg. However, no differences in mean FatOx (+2.5 (-2.4, 7.4) mg min-1), CarbOx (-6.1 (-17.4, 5.2) mg min-1) or RQ (-0.01 (-0.02, 0.01)) were observed between the two genotypes. CONCLUSIONS: We observed no evidence for associations of rs1421085 in FTO with FatOx and RQ. This indicates that the rs1421085-C allele in FTO induces obesity likely via other pathways than via reduced FatOx.

Both low circulating insulin-like growth factor-1 and high-density lipoprotein cholesterol are associated with hair loss in middle-aged women.

BACKGROUND: Multiple biomarkers have been associated with hair loss in women, but studies have shown inconsistent results. OBJECTIVES: We investigated the associations between markers of cardiovascular disease risk (e.g. serum lipid levels and hypertension) and ageing [e.g. 25-hydroxyvitamin D and insulin-like growth factor (IGF)] with hair loss in a population of middle-aged women. METHODS: In a random subgroup of 323 middle-aged women (mean age 61·5 years) from the Leiden Longevity Study, hair loss was graded by three assessors using the Sinclair scale; women with a mean score > 1·5 were classified as cases with hair loss. RESULTS: Every 1 SD increase in high-density lipoprotein (HDL) cholesterol was associated with a 0·65-times lower risk [95% confidence interval (CI) 0·46-0·91] of hair loss. For IGF-1 the risk was 0·68 times lower (95% CI 0·48-0·97) per 1 SD increase, independently of the other studied variables. Women with both IGF-1 and HDL cholesterol levels below the medians of the study population had a 3·47-times higher risk (95% CI 1·30-9·25) of having hair loss. CONCLUSIONS: Low HDL cholesterol and IGF-1 were associated with a higher risk of hair loss in women. However, further studies are required to infer causal relationships.

Lifestyle and youthful looks.

BACKGROUND: Lifestyle has been proven to have a dramatic effect on the risk of age-related diseases. The association of lifestyle and facial ageing has been less well studied. OBJECTIVES: To identify lifestyle factors that associate with perceived facial age in white north European men and women. METHODS: Lifestyle, facial wrinkling and perceived facial age were studied in two cross-sectional studies consisting of 318 Dutch men and 329 women aged 45-75 years who were part of the Leiden Longevity Study, and 162 English women aged 45-75 years who were nonsmokers. RESULTS: In Dutch men, smoking, having skin that went red in the sun, being outside in the sun most of the summer, sunbed use, wearing false teeth and not flossing teeth were all significantly associated (P < 0·05) with a total 9·3-year higher perceived facial age in a multivariate model adjusting for chronological age. In Dutch women, smoking, sunbathing, sunbed use, few remaining teeth and a low body mass index (BMI) were associated with a total 10·9-year higher perceived facial age. In English women, cleaning teeth only once a day, wearing false teeth, irregular skin moisturization and having skin that went red in the sun were associated with a total 9·1-year higher perceived facial age. Smoking and sunbed use were associated more strongly with wrinkling in women than in men. BMI, sun exposure and skincare were associated predominantly with perceived facial age via wrinkling, whereas oral care was associated via other facial features. CONCLUSIONS: Although associative in nature, these results support the notion that lifestyle factors can have long-term beneficial effects on youthful looks.

Serum insulin-like growth factor 1 and facial ageing: high levels associate with reduced skin wrinkling in a cross-sectional study.

BACKGROUND: Insulin-like growth factor (IGF)-1 is a growth factor that can influence fibroblast functioning, with effects including the inhibition of collagenases and the induction of collagen expression. OBJECTIVES: To assess whether serum IGF-1, IGF-binding protein (IGFBP)3 and the ratio between IGF-1 and IGFBP3, as a measure of IGF-1 bioavailability, are associated with facial ageing and skin wrinkling. METHODS: From a random sample comprising 617 subjects from the Leiden Longevity Study, perceived age and skin wrinkling were assessed from facial photographs, and IGF-1 and IGFBP3 were measured in serum. The associations were assessed using linear regression models, adjusted for chronological age, sex, body mass index, smoking and sun exposure. RESULTS: Across tertiles of the ratio of IGF-1 to IGFBP3, and after adjusting for all potential confounding factors, the mean perceived age decreased from 60·6 years in the lowest tertile to 59·5 years in the highest (P = 0·045). Similarly, the mean skin wrinkling grade decreased from 4·8 in the lowest tertile to 4·5 in the highest (P = 0·011). Adding skin wrinkling as a covariate in the analysis between IGF-1 and perceived age diminished this association. CONCLUSIONS: This study demonstrates that a higher ratio of IGF-1 to IGFBP3 associates with a lower perceived age, via its association with reduced skin wrinkling. Whether high IGF-1 levels actually delay the accumulation of skin wrinkling now needs investigating.

Biomarkers of the ageing immune system and their association with frailty - A systematic review.

INTRODUCTION: Ageing is associated with several physiological changes, including changes in the immune system. Age-related changes in the innate and adaptive immune system are thought to contribute to frailty. Understanding the immunological determinants of frailty could help to develop and deliver more effective care to older people. This systematic review aims to study the association between biomarkers of the ageing immune system and frailty. METHODS: The search strategy was performed in PubMed and Embase, using the keywords "immunosenescence", "inflammation", "inflammaging" and "frailty". We included studies that investigated the association of biomarkers of the ageing immune system and frailty cross-sectionally in older adults, without an active disease that affects immune parameters. Three independent researchers selected the studies and performed data extraction. Study quality was assessed using the Newcastle-Ottawa scale adapted for cross-sectional studies. RESULTS: A total of 44 studies, with a median number of 184 participants, was included. Study quality was good in 16 (36 %), moderate in 25 (57 %) and poor in 3 (7 %) of studies. The most frequently studied inflammaging biomarkers were IL-6, CRP and TNF-α. Associations with frailty were observed for increased levels of (i) IL-6 in 12 of 24 studies, (ii) CRP in 7 of 19 studies, and (ii) TNF-α in 4 of 13 studies. In none of the other studies were associations observed of frailty with these biomarkers. Different types of T-lymphocyte subpopulations were studied but each subset was studied only once, and the study sample sizes were low. CONCLUSION: Our review of 44 studies on the relation between immune biomarkers and frailty identified IL-6 and CRP as the biomarkers that were most consistently associated with frailty. T-lymphocyte subpopulations were investigated but too infrequently to draw strong conclusions yet, although initial results are promising. Additional studies are required in order to further validate these immune biomarkers in larger cohorts. Furthermore, prospective studies in more uniform settings and larger cohorts are needed to further investigate the association with immune candidate biomarkers for which potential associations with ageing and frailty were previously observed, before these can be used in clinical practice to help assess frailty and improve the care treatments of older patients.

Proton magnetic resonance spectroscopy shows lower intramyocellular lipid accumulation in middle-aged subjects predisposed to familial longevity.

Families predisposed to longevity show enhanced glucose tolerance and skeletal muscle insulin sensitivity compared with controls, independent of body composition and physical activity. Intramyocellular lipid (IMCL) accumulation in skeletal muscle has been associated with insulin resistance. Here, we assessed whether subjects enriched for familial longevity have lower IMCL levels. We determined IMCL levels in 48 subjects from the Leiden Longevity Study, comprising 24 offspring of nonagenarian siblings and 24 partners thereof as control subjects. IMCL levels were assessed noninvasively using short echo time proton magnetic resonance spectroscopy ((1)H-MRS) of the tibialis anterior muscle with a 7 Tesla human MR scanner. IMCL levels were calculated relative to the total creatine (tCr) CH3 signal. Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ). After correction for age, sex, BMI, and physical activity, offspring of long-lived nonagenarian siblings tended to show lower IMCL levels compared with controls (IMCL/tCr: 3.1 ± 0.5 vs. 4.5 ± 0.5, respectively, P = 0.051). In a pairwise comparison, this difference reached statistical significance (P = 0.038). We conclude that offspring of nonagenarian siblings predisposed to longevity show lower IMCL levels compared with environmentally matched control subjects. Future research should focus on assessing what mechanisms may explain the lower IMCL levels in familial longevity.

Interplay of circulating leptin and obesity in cognition and cerebral volumes in older adults.

We aimed to investigate whether circulating leptin and body mass index (BMI) associate independently with cognitive function (decline) and brain volumes using magnetic resonance imaging (MRI) in older individuals at risk of cardiovascular disease. We studied the cross-sectional and longitudinal associations in participants enrolled in the PROSPER study (Prospective Study of Pravastatin in the Elderly at Risk). Cognitive function was tested at baseline and repeated during a mean follow-up time of 3.2 years. Analyses were performed with multivariable (repeated) linear regression models and adjusted for demographics, cardiovascular risk-factors, and stratified by sex. We included 5623 dementia-free participants (52 % female, mean age 75 years) with a mean BMI of 26.9 (SD = 4.1). In a sub-study, 527 participants underwent brain MRI. At baseline, individuals with a BMI > 30 had a worse performance on the Stroop test (ß 5.0 s, 95 %CI 2.6;7.5) and larger volumes of the amygdala (ß 234 mm3, 95 %CI 3;464) and hippocampus (ß 590 mm3, 95 %CI 181;999), independent of intracranial volume and serum leptin levels, compared with individuals with the reference BMI (BMI 18-25 kg/m2). Per log ng/mL higher serum leptin, independent of BMI, a 135 mm3 (95 %CI 2;268) higher volume of the amygdala was found, but no association was observed with cognitive tests nor with other brain volumes. Stratification for sex did not materially change the results. Whereas higher BMI associated with worse cognitive function independent of leptin levels, our study provided evidence that leptin and BMI independently associate with amygdala volume suggesting potential distinct biological associations.

Variants of FOXO3 and RPA3 genes affecting IGF-1 levels alter the risk of development of primary osteoarthritis.

INTRODUCTION: Pathologically high growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels in patients with acromegaly are associated with arthropathy. Several studies highlight the potential role of the GH/IGF-1 axis in primary osteoarthritis (OA). We aimed to disentangle the role of IGF-1 levels in primary OA pathogenesis. METHODS: Patients from the Genetics osteoARthritis and Progression (GARP) Study with familial, generalized, symptomatic OA (n = 337, mean age: 59.8 ± 7.4 years, 82% female) were compared to Leiden Longevity Study (LLS) controls (n = 456, mean age: 59.8 ± 6.8 years, 51% female). Subjects were clinically and radiographically assessed, serum IGF-1 levels were measured, and 10 quantitative trait loci (QTL) in the FOXO3, IGFBP3/TNS3, RPA3, SPOCK2 genes, previously related to serum IGF-1 levels, were genotyped. Linear or binary logistic generalized estimating equation models were performed. RESULTS: Serum IGF-1 levels were increased in OA patients, with male patients exhibiting the strongest effect (males OR = 1.10 (1.04-1.17), P=0.002 vs females OR = 1.04 (1.01-1.07), P = 0.02). Independent of the increased IGF-1 levels, male carriers of the minor allele of FOXO3 QTL rs4946936 had a lower risk to develop hip OA (OR = 0.41 (0.18-0.90), P = 0.026). Additionally, independent of IGF-1 levels, female carriers of the minor alleles of RPA3 QTL rs11769597 had a higher risk to develop knee OA (OR = 1.90 (1.20-2.99), P = 0.006). CONCLUSION: Patients with primary OA had significantly higher IGF-1 levels compared to controls. Moreover, SNPs in the FOXO3 and RPA3 genes were associated with an altered risk of OA. Therefore, altered IGF-1 levels affect the development of OA, and are potentially the result of the pathophysiological OA process.

Ageing or cancer: a review on the role of caretakers and gatekeepers.

Ageing is due to the accumulation of damage, which arises because of evolved limitations in mechanisms for maintenance and repair. Accumulated damage may cause genomic instability, which in organisms with renewable tissues may result in cancer. To keep cancer at bay, two different tumour suppression mechanisms evolved: caretakers and gatekeepers. Caretakers protect the genome against mutations, while gatekeepers induce cell death or cell cycle arrest of potentially tumourigenic cells. It has been hypothesised that decreased activity of a caretaker may reduce life span, by increasing cancer risk, while the effects of increased activity of a gatekeeper on cancer risk and life span may be antagonistically pleiotropic. Apoptosis and senescence will promote early-life survival by curtailing the development of cancer, but may eventually limit longevity. This article reviews the evidence for this hypothesis. We conclude that several different findings indeed hint at an important role for gatekeeper mediated processes in ageing and its related pathologies. The relative contribution of apoptosis and senescence in specific age-related pathologies remains to be established.

C. elegans DAF-12, Nuclear Hormone Receptors and human longevity and disease at old age.

In Caenorhabditis elegans, DAF-12 appears to be a decisive checkpoint for many life history traits including longevity. The daf-12 gene encodes a Nuclear Hormone Receptor (NHR) and is member of a superfamily that is abundantly represented throughout the animal kingdom, including humans. It is, however, unclear which of the human receptor representatives are most similar to DAF-12, and what their role is in determining human longevity and disease at old age. Using a sequence similarity search, we identified human NHRs similar to C. elegans DAF-12 and found that, based on sequence similarity, Liver X Receptor A and B are most similar to C. elegans DAF-12, followed by the Pregnane X Receptor, Vitamin D Receptor, Constitutive Andosteron Receptor and the Farnesoid X Receptor. Their biological functions include, amongst others, detoxification and immunomodulation. Both are processes that are involved in protecting the body from harmful environmental influences. Furthermore, the DAF-12 signalling systems seem to be functionally conserved and all six human NHRs have cholesterol derived compounds as their ligands. We conclude that the DAF-12 signalling system seems to be evolutionary conserved and that NHRs in man are critical for body homeostasis and survival. Genomic variations in these NHRs or their target genes are prime candidates for the regulation of human lifespan and disease at old age.

Evidence-based medicine in older patients: how can we do better?

Evidence-based medicine (EBM) aims to integrate three elements in patient care: the patient situation, scientific evidence, and the doctors' expertise. This review aims 1) to assess how these elements are systematically different in older patients and 2) to propose strategies how to improve EBM in older patients. The ageing process systematically affects all three elements that constitute EBM. First, ageing changes the physiology of the older body, makes the patient more vulnerable with more multimorbidity and polypharmacy and affects somatic, psychological and social function. The heterogeneity of older patients may lead to overtreatment of vulnerable and undertreatment of fit older patients. Second, representative older patients are underrepresented in clinical studies and endpoints studied may not reflect the specific needs of older patients. Third, adequate clinical tools and schooling are lacking to aid physicians in clinical decision-making. Strategies to improve elements of EBM include: first systematically acknowledging that physical, mental and social function may reveal patients vulnerability and specific treatment goals. Second, clinical studies specifically targeting more representative older patients and studying endpoints relevant to older patients are warranted. Finally, teaching of physicians may increase their experience and expertise in treating older patients. In conclusion, in older patients the same elements constitute EBM, but the elements need tailoring to the older patient. In the clinic, a thorough assessment of individual patient preferences and physical, mental and social functioning in combination with increased level of experience of the doctor can increase the quality of EBM in older patients.

A simple and versatile method for frequent 24 h blood sample collection in healthy older adults.

Repeated 24 h blood sampling, which is required for time series analyses of metabolites and/or hormones that show strong fluctuations in blood concentration over time, has a higher failure rate in older adults. We tailored existing venipuncture protocols toward use for 24 h blood sampling (sampling frequency of 10 min) in older adults. The following modifications were made: •Pre-sampling: evidence based risk assessment of older adults.•During sampling:•Ultrasound-guided identification and characterisation of veins.•Use of 20-gauge arterial catheter with guide wire for venous access.•Measures to prevent and/or reduce unidirectional blood flow (fluid flow into but not out of the vein) included:•Use of hot water bottles to dilate veins.•Use of small gauge syringes, shortening of the extension line, and slowing of the blood withdrawal rate to reduce pressure on veins.•Stimulation of movement of the arm or retraction of the IV cannula to relieve mechanical flow obstruction.•Post-sampling: prevention of bruising and prolonged bleeding.

Human longevity is characterised by high thyroid stimulating hormone secretion without altered energy metabolism.

Few studies have included subjects with the propensity to reach old age in good health, with the aim to disentangle mechanisms contributing to staying healthier for longer. The hypothalamic-pituitary-thyroid (HPT) axis maintains circulating levels of thyroid stimulating hormone (TSH) and thyroid hormone (TH) in an inverse relationship. Greater longevity has been associated with higher TSH and lower TH levels, but mechanisms underlying TSH/TH differences and longevity remain unknown. The HPT axis plays a pivotal role in growth, development and energy metabolism. We report that offspring of nonagenarians with at least one nonagenarian sibling have increased TSH secretion but similar bioactivity of TSH and similar TH levels compared to controls. Healthy offspring and spousal controls had similar resting metabolic rate and core body temperature. We propose that pleiotropic effects of the HPT axis may favour longevity without altering energy metabolism.

Gerontology and geriatrics in Dutch medical education.

BACKGROUND: The world population is ageing and healthcare services require trained staff who can address the needs of older patients. In this study we determined how current medical education prepares Dutch students of medicine in the field of Gerontology and Geriatrics (G&G). METHODS: Using a checklist of the essentials of G&G, we assessed Dutch medical education on three levels. On the national level we analysed the latest National Blueprint for higher medical education (Raamplan artsopleiding 2009). On the faculty level we reviewed medical curricula on the basis of interviews with program directors and inspection of course materials. On the student level we assessed the topics addressed in the questions of the cross-institutional progress test (CIPT). RESULTS: The National Bluepr int contains few specific G&G objectives. Obligatory G&G courses in medical schools on average amount to 2.2% of the total curriculum measured as European Credit Transfer System units (ECTS). Only two out of eight medical schools have practical training during the Master phase in the form of a clerkship in G&G. In the CIPT, on average 1.5% of questions cover G&G. CONCLUSION: Geriatric education in the Netherlands does not seem to be in line with current demographic trends. The National Blueprint falls short of providing sufficiently detailed objectives for education on the care of older people. The geriatric content offered by medical schools is varied and incomplete, and students are only marginally tested on their knowledge of G&G in the CIPT.

Diagnostic criteria for sarcopenia relate differently to insulin resistance.

Skeletal muscle is important in insulin-stimulated glucose uptake. Sarcopenia is, therefore, a possible risk factor for insulin resistance. Currently, different diagnostic criteria for sarcopenia include low muscle mass, muscle strength, and walking speed. We assessed these muscle characteristics in relation to insulin resistance in nondiabetics. This cross-sectional study included 301 nondiabetics, mean age 65.9 years. Area under curve (AUC) calculations of insulin and glucose from a 2-h oral glucose tolerance test (OGTT) and homeostasis model assessment of insulin resistance (HOMA-IR) were used as measures of insulin resistance. Muscle characteristics were relative muscle mass (total or appendicular lean mass (ALM) as percentage of body mass), absolute muscle mass (ALM/height(2) and total lean mass), handgrip strength, and walking speed. All muscle characteristics were standardized and analyzed in linear regression models, stratified by gender. For both males and females, relative muscle mass was inversely associated with AUC insulin, AUC glucose, and HOMA-IR (ALM percentage all p ≤ 0.004). Absolute muscle mass was positively associated with AUC insulin and HOMA-IR (ALM/height(2) all p < 0.001) but not with AUC glucose. Adjustments for fat mass attenuated aforementioned associations. There were no associations between handgrip strength and insulin resistance. Walking speed was inversely associated with AUC insulin in males (p = 0.032). The association between muscle characteristics and insulin resistance was strongest for relative muscle mass. Diagnostic criteria for sarcopenia relate differently to insulin resistance. The role of muscle tissue as an internal glucose-regulating organ is better reflected by relative muscle mass than by absolute muscle mass, muscle strength, or walking speed.