Non-Dietary Correlates and Determinants of Plasma Lutein and Zeaxanthin Concentrations in the Irish Population

Association of vitamins, minerals, and lead with lipoprotein(a) in a cross-sectional cohort of US adults

Lipoprotein(a)(Lp[a]) is a low-density lipoprotein-cholesterol (LDL-C)-like particle with potent pro-atherothrombotic properties. The association of Lp(a) with several circulating factors, including vitamins, remains unresolved. We performed an observational analysis using the National Health and Nutrition Examination Survey III cohort, a cohort used to monitor the nutrition status of US-citizens. We used multivariable linear regression to test associations of Lp(a) and LDL-C with levels of serum vitamins and minerals and whole-blood lead. Analyses controlled for factors known to associate with Lp(a) (age, sex, race/ethnicity, statin use, hemoglobin A1c, body mass index, hypertension, diabetes, glomerular filtration rate, alcohol intake, and saturated fat intake). LDL-C was corrected for Lp(a) mass. Multiple sensitivity tests were performed, including considering factors as categorical variables (deficient, normal, elevated). Among 7,662 subjects, Lp(a) correlated (β-coefficient) positively (change per 1 conventional unit increase) with carotenoids (lycopene (0.17(0.06,0.28), p=0.005), lutein (0.19(0.07,0.30), p=0.002), β-cryptoxanthin (0.21(0.05,0.37), p=0.01), β-carotene (0.05(0.02,0.09), p=0.003), and α-carotene (0.15(0.01,0.30), p=0.04)) and lead (0.54(0.03,1.05), p=0.04) levels when tested as continuous variables. LDL-C had similar associations. Lp(a) did not associate with vitamins A, B12, C, or E retinyl esters, folate, RBC-folate, selenium, ferritin, transferrin saturation, or calcium. With factors as categorical variables, Lp(a) but not LDL-C negatively associated with elevated vitamin B12 (-5.41(-9.50, -1.53), p=0.01) and folate (-2.86(-5.09, -0.63), p=0.01). In conclusion, Lp(a) associated similarly to LDL-C when vitamins, minerals, and lead were tested as continuous variables, while only Lp(a) correlated with vitamin B12 and folate when tested as categorical variables. These observations are hypotheses generating and require further studies to determine causality.

Plasma lutein and zeaxanthin concentrations associated with musculoskeletal health and incident frailty in The Irish Longitudinal Study on Ageing (TILDA)

INTRODUCTION

Lutein and zeaxanthin are diet-derived carotenoids that are proposed to help mitigate frailty risk and age-related declines in musculoskeletal health via their anti-oxidant and anti-inflammatory properties. Therefore, this study aimed to investigate the association between lutein and zeaxanthin status and indices of musculoskeletal health and incident frailty among community-dwelling adults aged ≥50 years in the Irish Longitudinal Study on Ageing (TILDA).

METHODS

Cross-sectional analyses (n = 4513) of plasma lutein and zeaxanthin concentrations and grip strength, usual gait speed, timed up-and-go (TUG), probable sarcopenia (defined as grip strength <27 kg in men, <16 kg in women), and bone mass (assessed using calcaneal broadband ultrasound stiffness index) were performed at Wave 1 (2009-2011; baseline). In the longitudinal analyses (n = 1425-3100), changes in usual gait speed (at Wave 3, 2014-2015), grip strength (Wave 4, 2016) and TUG (at Wave 5, 2018), incident probable sarcopenia (at Wave 4) and incident frailty (Fried's phenotype, Frailty Index, FRAIL Scale, Clinical Frailty Scale-classification tree, at Wave 5) were determined. Data were analysed using linear and ordinal logistic regression, adjusted for confounders.

RESULTS

Cross-sectionally, plasma lutein and zeaxanthin concentrations were positively associated with usual gait speed (B [95 % CI] per 100-nmol/L higher concentration: Lutein 0.59 [0.18, 1.00], Zeaxanthin 1.46 [0.37, 2.55] cm/s) and inversely associated with TUG time (Lutein -0.07 [-0.11, -0.03], Zeaxanthin -0.14 [-0.25, -0.04] s; all p < 0.01), but not with grip strength or probable sarcopenia (p > 0.05). Plasma lutein concentration was positively associated with bone stiffness index (0.54 [0.15, 0.93], p < 0.01). Longitudinally, among participants who were non-frail at Wave 1, higher plasma lutein and zeaxanthin concentrations were associated lower odds of progressing to a higher frailty category (e.g. prefrailty or frailty) by Wave 5 (ORs 0.57-0.89, p < 0.05) based on the Fried's phenotype, FRAIL Scale and the Clinical Frailty Scale, and in the case of zeaxanthin, Frailty Index. Neither plasma lutein nor zeaxanthin concentrations were associated with changes in musculoskeletal indices or incident probable sarcopenia (p > 0.05).

CONCLUSION

Higher plasma lutein and zeaxanthin concentrations at baseline were associated with a reduced likelihood of incident frailty after ~8 years of follow up. Baseline plasma lutein and zeaxanthin concentrations were also positively associated with several indices of musculoskeletal health cross-sectionally but were not predictive of longitudinal changes in these outcomes over 4-8 years.

Association of Plasma Carotenoid and Malondialdehyde Levels with Physical Performance in Korean Adolescents

Increased oxidative stress has been shown to lead to muscle damage and reduced physical performance. The antioxidant mechanism is most likely to reduce these relationships, but in the context of the action of carotenoids, more research is needed. This study aimed to investigate whether carotenoids modify the association between plasma malondialdehyde (MDA) and physical performance in Korean adolescents. The study sample consisted of 381 adolescents (164 boys, 217 girls) aged 13–18, who participated in the 2018 National Fitness Award Project. We quantified α-carotene, β-carotene, β-cryptoxanthin, lutein, zeaxanthin, lycopene, and MDA levels in plasma using HPLC with photodiode array detection. Among boys but not girls, plasma MDA level was negatively associated (β = −0.279, p = 0.0030) with total plasma carotenoid levels and marginally negatively associated (β = −0.907, p = 0.0876) with absolute hand grip strength. After adjustment for covariates in boys, the MDA level was negatively associated with absolute hand grip strength and relative hand grip strength; this association was observed only in groups with individual carotenoid and total carotenoid values below the median. These findings support a significant association between plasma MDA level and hand grip strength, and this association has been potentially modified by plasma levels of carotenoids in Korean male adolescents.

Biomarker Signatures of Two Phenotypical Prefrailty Types in the Irish Longitudinal Study on Ageing

We investigated the biomarker signatures of two previously reported phenotypical prefrailty (PF) types in the first wave of The Irish Longitudinal Study on Ageing (TILDA): PF1 (unexplained weight loss and/or exhaustion) and PF2 (one or two among slowness, weakness, and low physical activity). Binary logistic regression models evaluated the independent associations between available plasma biomarkers and each PF type (compared to robust and compared to each other), while adjusting for age, sex, and education. A total of 5307 participants were included (median age 61 years, 53% women) of which 1473 (28%) were prefrail (469 PF1; 1004 PF2), 171 were frail, and 3663 were robust. The PF2 median age was eight years older than the PF1 median age. Higher levels of lutein and zeaxanthin were independently associated with the lower likelihood of PF1 (OR: 0.77, p < 0.001 and OR: 0.81, p < 0.001, respectively). Higher cystatin C was associated with PF1 (OR: 1.23, p = 0.001). CRP (OR: 1.19, p < 0.001), cystatin C (OR: 1.36, p < 0.001), and HbA1c (OR: 1.18, p < 0.001) were independently associated with PF2, while a higher total (OR: 0.89, p = 0.004) and HDL (OR: 0.87, p < 0.001) cholesterol seemed to be PF2-protective. While PF1 seemed to be inversely associated with serum carotenoid concentrations and hence has an oxidative signature, PF2 seemed to have pro-inflammatory, hyperglycemic, and hypolipidemic signatures. Both PF types were associated with higher cystatin C (lower kidney function), but no biomarkers significantly distinguished PF1 vs. PF2. Further research should elucidate whether therapies for different PF types may require targeting of different biological pathways.

Whey- and Soy Protein Isolates Added to a Carrot-Tomato Juice Alter Carotenoid Bioavailability in Healthy Adults

Recent findings suggested that proteins can differentially affect carotenoid bioaccessibility during gastro-intestinal digestion. In this crossover, randomized human trial, we aimed to confirm that proteins, specifically whey- and soy-protein isolates (WPI/SPI) impact postprandial carotenoid bioavailability. Healthy adults (n = 12 males, n = 12 females) were recruited. After 2-week washout periods, 350 g of a tomato-carrot juice mixture was served in the absence/presence of WPI or SPI (50% of the recommended dietary allowance, RDA ≈ 60 g/d). Absorption kinetics of carotenoids and triacylglycerols (TAGs) were evaluated via the triacylglycerol-rich lipoprotein (TRL) fraction response, at timed intervals up to 10 h after test meal intake, on three occasions separated by 1 week. Maximum TRL-carotenoid concentration (C_max) and corresponding time (T_max) were also determined. Considering both genders and carotenoids/TAGs combined, the estimated area under the curve (AUC) for WPI increased by 45% vs. the control (p = 0.018), to 92.0 ± 1.7 nmol × h/L and by 57% vs. SPI (p = 0.006). Test meal effect was significant in males (p = 0.036), but not in females (p = 0.189). In males, significant differences were found for phytoene (p = 0.026), phytofluene (p = 0.004), α-carotene (p = 0.034), and β-carotene (p = 0.031). C_max for total carotenoids (nmol/L ± SD) was positively influenced by WPI (135.4 ± 38.0), while significantly lowered by SPI (89.6 ± 17.3 nmol/L) vs. the control (119.6 ± 30.9, p < 0.001). T_max did not change. The results suggest that a well-digestible protein could enhance carotenoid bioavailability, whereas the less digestible SPI results in negative effects. This is, to our knowledge, the first study finding effects of proteins on carotenoid absorption in humans.

Environmental and Nutritional Determinants of Macular Pigment in a Mexican Population

Purpose

The carotenoids lutein (L), zeaxanthin (Z), and meso-zeaxanthin deposit at the macula as macular pigment (MP) and provide visual benefits and protection against macular diseases. The present study investigated MP, its nutritional and environmental determinants, and its constituent carotenoids in serum from a Mexican sample, in healthy participants and with metabolic diseases. Additionally, we compared these variables with an Irish sample.

Methods

MP was measured in 215 subjects from a rural community in Mexico with dual-wavelength autofluorescence imaging reported as MP optical volume (MPOV). Dietary intake and serum concentrations of L and Z were evaluated.

Results

The mean MPOV was 8429 (95% confidence interval, 8060-8797); range. 1171-15,976. The mean L and Z serum concentrations were 0.25 ± 0.15 µmol/L and 0.09 ± 0.04 µmol/L, respectively. The MPOV was positively correlated with L and Z serum concentrations (r = 0.347; P < 0.001 and r = 0.311; P < 0.001, respectively), but not with L + Z dietary estimates. Subjects with daily sunlight exposure of more than 50% were found to have significantly higher MPOV than those with less than 50% (P = 0.005). MPOV and serum concentrations of L and Z were significantly higher in the Mexican sample compared with the Irish sample, but this difference was not reflected in dietary analysis.

Conclusions

These new data from a Mexican sample provide evidence of the multifactorial interactions and environmental determinants of MP such as sunlight exposure and dietary patterns. These findings will be essential for future studies in Mexico for eye health, visual function, and ocular pathology.

From carotenoid intake to carotenoid blood and tissue concentrations - implications for dietary intake recommendations

There is uncertainty regarding carotenoid intake recommendations, because positive and negative health effects have been found or are correlated with carotenoid intake and tissue levels (including blood, adipose tissue, and the macula), depending on the type of study (epidemiological vs intervention), the dose (physiological vs supraphysiological) and the matrix (foods vs supplements, isolated or used in combination). All these factors, combined with interindividual response variations (eg, depending on age, sex, disease state, genetic makeup), make the relationship between carotenoid intake and their blood/tissue concentrations often unclear and highly variable. Although blood total carotenoid concentrations <1000 nmol/L have been related to increased chronic disease risk, no dietary reference intakes (DRIs) exist. Although high total plasma/serum carotenoid concentrations of up to 7500 nmol/L are achievable after supplementation, a plateauing effect for higher doses and prolonged intake is apparent. In this review and position paper, the current knowledge on carotenoids in serum/plasma and tissues and their relationship to dietary intake and health status is summarized with the aim of proposing suggestions for a "normal," safe, and desirable range of concentrations that presumably are beneficial for health. Existing recommendations are likewise evaluated and practical dietary suggestions are included.

Standardizing the Assessment of Macular Pigment Using a Dual-Wavelength Autofluorescence Technique

PURPOSE

It is essential to have an appropriate measure to assess macular pigment (MP) that can provide an accurate, valid, and reliable representation of the MP within the macula. The aim of this study was to describe and introduce MP optical volume (MPOV) as an optimal value for reporting MP.

METHODS

Three hundred ninety-three subjects were analyzed using the Heidelberg Spectralis with the investigational MP optical density (MPOD) module to measure MPOV and MPOD at four foveal eccentricities (0.23°, 0.51°, 0.98°, 1.76° [7° as reference point]). Lutein (L) and zeaxanthin (Z) dietary intake and serum concentrations were evaluated.

RESULTS

MPOV mean was 5094 (95%CI, 4877-5310); range: 527 to 10,652. MPOV was inversely correlated with body mass index and positively correlated with education (r = -0.156, P = 0.002 and r = 0.124, P = 0.014, respectively). Serum concentrations of L and Z were positively correlated with MPOV (r = 0.422, P < 0.001 and r = 0.285, P < 0.001, respectively). MPOV was positively correlated to MPOD at all measured eccentricities, with the strongest agreement at 1.76° (r = 0.906, P < 0.001). Serum concentrations of L and Z, BMI, education, and age (P < 0.001) were found to be significant predictors of MPOV.

CONCLUSIONS

The Spectralis MPOV measurement provided a comprehensive and detailed evaluation of the MP profile. The Spectralis MPOV should be considered a preferred metric for the assessment of MP.

TRANSLATIONAL RELEVANCE

Applying a standardized method for the assessment and report of MP will allow to fully derive meaning from observational studies and to successfully implement this MP measurement technique in research and clinical settings.

Circulating Micronutrient Biomarkers Are Associated With 3 Measures of Frailty: Evidence From the Irish Longitudinal Study on Ageing

OBJECTIVES

To examine the associations between 3 frailty instruments and circulating micronutrients in a large representative sample of older adults.

DESIGN

Cross-sectional data from a nationally representative cohort study conducted between October 2009 and July 2011.

PARTICIPANTS AND SETTING

Adults age ≥50 years (n = 4068) living in the community in Ireland.

MEASUREMENTS

Circulating micronutrients (lutein, zeaxanthin, folate, vitamin B-12, and vitamin D) were measured, transformed, and standardized. Frailty was assessed using the Frailty Phenotype, the Frailty Index, and the FRAIL Scale (fatigue, resistance, ambulation, illnesses, and loss of weight), instruments. Multinomial logistic regression determined associations between micronutrients and prefrailty or frailty. Models were adjusted for sociodemographic, lifestyle, health, and seasonal factors.

RESULTS

Adjusting for age, sex, and educational attainment, all 3 measures of frailty were associated with lower levels of lutein [relative risk ratios (RRRs): 0.43‒0.63], zeaxanthin (RRRs: 0.49‒0.63), and vitamin D (RRRs: 0.51‒0.75), and with the accumulation of micronutrient insufficiencies (RRRs: 1.42‒1.90). Attenuated but significant associations were also observed with all measures of prefrailty for lutein, vitamin D, and number of micronutrient insufficiencies. The associations with frailty persisted following additional adjustment for social, lifestyle, and health and seasonal factors, and following multiple test correction.

CONCLUSIONS AND IMPLICATIONS

We have presented the most consistent evidence in the largest study to date that micronutrient concentrations are associated with prefrailty and frailty in older adults. Our data suggest that low micronutrient status has potential as an easily modifiable marker and intervention target for frailty and supports further investigation into micronutrient supplementation and fortification to prevent frailty and disability among older adults.

Correlates of the difference in plasma carotenoid concentrations between men and women

Health professionals consider the evaluation of eating habits to be challenging, given the potential biases of dietary questionnaires based on self-reported data. Circulating carotenoid concentrations are reliable biomarkers of dietary carotenoid intake and could be useful in the validation of dietary assessment tools. However, there is a sex difference in circulating carotenoids, with women displaying higher concentrations compared with men independent of intake. The aim of the present study was to identify the correlates of plasma carotenoid concentrations among men (n 155) and women (n 110) enrolled in six fully controlled dietary interventions with varying dietary carotenoid intakes. We looked at the associations of post-intervention fasting plasma carotenoid concentrations (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene and zeaxanthin) with physical and metabolic characteristics. We found that increased body weight (r -0·47, P&lt;0·0001) and waist circumference (r -0·46, P&lt;0·0001) were associated with lower plasma total carotenoid concentrations, while elevated plasma LDL-cholesterol (r 0·49, P&lt;0·0001) and HDL-cholesterol (r 0·50, P&lt;0·0001) concentrations were correlated with higher total carotenoids in plasma. Women had significantly higher plasma total carotenoid concentrations compared with men, despite significantly lower dietary carotenoid intake. Adjustment of circulating carotenoid concentrations for plasma HDL-cholesterol eliminated sex difference in plasma carotenoid concentrations. Our results suggest that physical characteristics as well as plasma lipids are associated with circulating carotenoid concentrations and that these variables should be taken into account when using plasma carotenoids as biomarkers for food intake in men and women.

Genetic and Common Environmental Contributions to Familial Resemblances in Plasma Carotenoid Concentrations in Healthy Families

Carotenoids have shown an interindividual variability that may be due to genetic factors. The only study that has reported heritability of serum α- and β-carotene has not considered the environmental component. This study aimed to estimate the contribution of both genetic and common environmental effects to the variance of carotenoid concentrations and to test whether their phenotypic correlations with cardiometabolic risk factors are explained by shared genetic and environmental effects. Plasma carotenoid concentrations (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene, zeaxanthin, and total carotenoids) of 48 healthy subjects were measured. Heritability estimates of carotenoid concentrations were calculated using the variance component method. Lutein and lycopene showed a significant familial effect (p = 6 × 10^-6 and 0.0043, respectively). Maximal heritability, genetic heritability, and common environmental effect were computed for lutein (88.3%, 43.8%, and 44.5%, respectively) and lycopene (45.2%, 0%, and 45.2%, respectively). Significant phenotypic correlations between carotenoid concentrations and cardiometabolic risk factors were obtained for β-cryptoxanthin, lycopene, and zeaxanthin. Familial resemblances in lycopene concentrations were mainly attributable to common environmental effects, while for lutein concentrations they were attributable to genetic and common environmental effects. Common genetic and environmental factors may influence carotenoids and cardiometabolic risk factors, but further studies are needed to better understand the potential impact on disease development.