Serum Phosphate, BMI, and Body Composition of Middle-Aged and Older Adults: A Cross-Sectional Association Analysis and Bidirectional Mendelian Randomization Study.

BACKGROUND: Observational studies have reported associations between serum phosphate and BMI in specific clinical settings, but the nature of this relation in the general population is unclear. OBJECTIVES: The aim of this study was twofold: to investigate the association between serum phosphate and BMI and body composition, as well as to explore evidence of causality through a bidirectional one-sample Mendelian randomization (MR) in the population-based Rotterdam Study (RS). METHODS: Observational associations between phosphate (mg/dL) and BMI, lean mass, and fat percentage (fat%), estimated by DXA, were analyzed using multivariable regression models in 9202 participants aged 45-100 y from 3 RS cohorts. The role of serum leptin was examined in a subgroup of 1089 participants. For MR analyses, allele scores with 6 single-nucleotide polymorphisms (SNPs) for phosphate and 905 SNPs for BMI were constructed in 7983 participants. RESULTS: Phosphate was inversely associated with BMI in the total population (ß: -0.89; 95% CI: -1.17, -0.62), and stronger in women (ß: -1.92; 95% CI: -2.20, -1.65) than in men (ß: -0.37; 95% CI: -0.68, -0.06) (P-interaction < 0.05). Adjustment for leptin did not change results in men. In women, adjustment for leptin attenuated the association, but it was not abolished (ß: -0.94; 95% CI: -1.45, -0.42). Phosphate was inversely associated with fat%, but not with lean mass, in both sexes. MR analyses suggested a causal effect of BMI on serum phosphate (ß: -0.01; 95% CI: -0.02, 0.00) but not vice versa. CONCLUSIONS: Serum phosphate was inversely associated with BMI and fat% in a population-based study of middle-aged and older adults, with a stronger effect in women than in men. Adjusting for leptin attenuated this relation in women only. MR results suggest a causal effect of BMI on phosphate but not vice versa. An underlying sex dimorphism in phosphate homeostasis should be further explored.

Low-Frequency Synonymous Coding Variation in CYP2R1 Has Large Effects on Vitamin D Levels and Risk of Multiple Sclerosis.

Vitamin D insufficiency is common, correctable, and influenced by genetic factors, and it has been associated with risk of several diseases. We sought to identify low-frequency genetic variants that strongly increase the risk of vitamin D insufficiency and tested their effect on risk of multiple sclerosis, a disease influenced by low vitamin D concentrations. We used whole-genome sequencing data from 2,619 individuals through the UK10K program and deep-imputation data from 39,655 individuals genotyped genome-wide. Meta-analysis of the summary statistics from 19 cohorts identified in CYP2R1 the low-frequency (minor allele frequency = 2.5%) synonymous coding variant g.14900931G>A (p.Asp120Asp) (rs117913124[A]), which conferred a large effect on 25-hydroxyvitamin D (25OHD) levels (-0.43 SD of standardized natural log-transformed 25OHD per A allele; p value = 1.5 × 10-88). The effect on 25OHD was four times larger and independent of the effect of a previously described common variant near CYP2R1. By analyzing 8,711 individuals, we showed that heterozygote carriers of this low-frequency variant have an increased risk of vitamin D insufficiency (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 1.78-2.78, p = 1.26 × 10-12). Individuals carrying one copy of this variant also had increased odds of multiple sclerosis (OR = 1.4, 95% CI = 1.19-1.64, p = 2.63 × 10-5) in a sample of 5,927 case and 5,599 control subjects. In conclusion, we describe a low-frequency CYP2R1 coding variant that exerts the largest effect upon 25OHD levels identified to date in the general European population and implicates vitamin D in the etiology of multiple sclerosis.

Serum 25-hydroxyvitamin D3 is associated with advanced glycation end products (AGEs) measured as skin autofluorescence: The Rotterdam Study.

Advanced glycation end products (AGEs) accumulate in tissues with aging and may influence age-related diseases. They can be estimated non-invasively by skin autofluorescence (SAF) using the AGE Reader™. Serum 25-hydroxyvitamin D3 (25(OH)D3) may inhibit AGEs accumulation through anti-oxidative and anti-inflammatory properties but evidence in humans is scarce. The objective was to investigate the association between serum 25(OH)D3 and SAF in the population-based cohort study. Serum 25(OH)D3 and other covariates were measured at baseline. SAF was measured on average 11.5 years later. Known risk factors for AGE accumulation such as higher age, BMI, and coffee intake, male sex, smoking, diabetes, and decreased renal function were measured at baseline. Linear regression models were adopted to explore the association between 25(OH)D3 and SAF with adjustment for confounders. Interaction terms were tested to identify effect modification. The study was conducted in the general community. 2746 community-dwelling participants (age ≥ 45 years) from the Rotterdam Study were included. Serum 25(OH)D3 inversely associated with SAF and explained 1.5% of the variance (unstandardized B = - 0.002 (95% CI[- 0.003, - 0.002]), standardized ß = - 0.125), independently of known risk factors and medication intake. The association was present in both diabetics (B = - 0.004 (95% CI[- 0.008, - 0.001]), ß = - 0.192) and non-diabetics (B = - 0.002 (95% CI[- 0.003, - 0.002]), ß = - 0.122), both sexes, both smokers and non-smokers and in each RS subcohort. Serum 25(OH)D3 concentration was significantly and inversely associated with SAF measured prospectively, also after adjustment for known risk factors for high SAF and the number of medication used, but the causal chain is yet to be explored in future studies.Clinical Trial Registry (1) Netherlands National Trial Register: Trial ID: NTR6831 ( http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=6831 ). (2) WHO International Clinical Trials Registry Platform: under shared catalogue number NTR6831 ( www.who.int/ictrp/network/primary/en/ ).

Serum phosphate levels are related to all-cause, cardiovascular and COPD mortality in men.

Hyperphosphatemia has been associated with increased mortality in chronic kidney disease but the nature of such a relation in the general population is unclear. To investigate the association between phosphate (P) levels and all-cause and cause-specific mortality, we assessed two cohorts from the Rotterdam Study, with follow-up of 14.5 (RS-I) and 10.9 (RS-II) years until January 2012 with availability of fasting phosphate levels. Deaths were classified according to International Classification of Diseases into 7 groups: cardiovascular, cancer, infections, external, dementia, chronic lung diseases and other causes. Sex-stratified Weibull and competing-risks models were adjusted for age, BMI and smoking. Hazard ratios are expressed per 1 mg/dL increase in phosphate levels. The total number of participants included 3731 (RS-I, 2154 women) and 2494 (RS-II, 1361 women) subjects. The main outcome measures were all-cause and cause-specific mortality. A significant positive association was found between phosphate and all-cause mortality in men (pooled HR (95% CI): 1.46 (1.26-1.69)) but not in women (0.90 (0.77-1.05)). In men, higher phosphate increased the risk for cardiovascular mortality (1.66 (1.29-2.14)), other causes (1.67 (1.16-2.40)) and chronic lung disease mortality (1.94 (1.02-3.72)), the latter driven by mortality due to chronic obstructive pulmonary disease (COPD) (4.44 (2.08-9.49)). No relations were found for mortality due to infections, cancer, dementia or external causes. In conclusion, serum P is associated with increased all-cause, cardiovascular and COPD mortality in men but not women. The association with COPD mortality is novel and needs further research on underlying mechanisms.

PLS3 mutations in X-linked osteoporosis with fractures.

Plastin 3 (PLS3), a protein involved in the formation of filamentous actin (F-actin) bundles, appears to be important in human bone health, on the basis of pathogenic variants in PLS3 in five families with X-linked osteoporosis and osteoporotic fractures that we report here. The bone-regulatory properties of PLS3 were supported by in vivo analyses in zebrafish. Furthermore, in an additional five families (described in less detail) referred for diagnosis or ruling out of osteogenesis imperfecta type I, a rare variant (rs140121121) in PLS3 was found. This variant was also associated with a risk of fracture among elderly heterozygous women that was two times as high as that among noncarriers, which indicates that genetic variation in PLS3 is a novel etiologic factor involved in common, multi-factorial osteoporosis.

Diuretic Use and Serum Phosphate: Rotterdam Study and UK Biobank.

Purpose: Hypophosphatemia (serum phosphate < 0.80 mmol/L) leads to musculoskeletal complaints. The most common drugs linked to hypophosphatemia are thiazide and loop diuretics, but studies in the general population are lacking. Our aim was to study associations between diuretic use and serum phosphate in the Rotterdam Study (RS), a population-based cohort study, with replication in UK Biobank (UKBB). Methods: Associations between thiazide and loop diuretic use and serum phosphate and odds of hypophosphatemia were analyzed with cross-sectional multivariate linear and logistic regression in participants without chronic kidney disease in the RS and UKBB. Analyses were adjusted for age, sex, and body mass index (BMI) and pooled in 3 RS cohorts with further adjustment for cohort and serum potassium, which was not available in UKBB. Results: Thiazide diuretics were associated with lower serum phosphate in both sexes. This association lost significance in RS females after adjustment for BMI and in males after adjustment for serum potassium. Thiazide diuretics increased odds of hypophosphatemia in females in both cohorts and in males in UKBB only. Loop diuretics were associated with lower serum phosphate in females but not males. Adjustment for BMI attenuated these associations. Associations between loop diuretics and increased odds of hypophosphatemia in females lost significance after BMI adjustment. Conclusion: Thiazides, but not loop diuretics, and increased BMI and decreased serum potassium should be considered as contributing factors in subjects with hypophosphatemia. Further studies are needed to replicate the findings and elucidate the potential role of hypokalemia as a mediator of this effect.

Exogenous Klotho Extends Survival in COVID-19 Model Mice.

A striking feature of COVID-19 disease is the broad spectrum of risk factors associated with case severity, as well as the diversity of clinical manifestations. While no central agent has been able to explain the pathogenesis of SARS-CoV-2 infection, the factors that most robustly correlate with severity are risk factors linked to aging. Low serum levels of Klotho, an anti-aging protein, strongly correlate with the pathogenesis of the same risk factors and manifestations of conditions similar to those expressed in severe COVID-19 cases. The current manuscript presents original research on the effects of the exogenous application of Klotho, an anti-aging protein, in COVID-19 model mice. Klotho supplementation resulted in a statistically significant survival benefit in parametric and non-parametric models. Further research is required to elucidate the mechanistic role Klotho plays in COVID-19 pathogenesis as well as the possible modulation SARS-CoV-2 may have on the biological aging process.

Sexual dimorphisms in serum calcium and phosphate concentrations in the Rotterdam Study.

Sex differences in serum phosphate and calcium have been reported but the exact nature and underlying regulatory mechanisms remain unclear. We aimed to compare calcium and phosphate concentrations between sexes, and explore potential covariates to elucidate underlying mechanisms of sex differences in a prospective, population-based cohort study. Pooled data of subjects > 45 years from three independent cohorts of the Rotterdam Study (RS) were used: RS-I-3 (n = 3623), RS-II-1 (n = 2394), RS-III-1 (n = 3241), with separate analyses from an additional time point of the first cohort RS-I-1 (n = 2688). Compared to men, women had significantly higher total serum calcium and phosphate concentrations which was not explained by BMI, kidney function nor smoking. Adjustment for serum estradiol diminished sex differences in serum calcium while adjustment for serum testosterone diminished sex differences in serum phosphate. Adjustment for vitamin D and alkaline phosphatase did not change the association between sex and calcium or phosphate in RS-I-1. In the sex-combined group, both serum calcium and phosphate decreased with age with a significant interaction for sex differences for serum calcium but not phosphate. In sex-stratified analyses, serum estradiol but not testosterone was inversely associated with serum calcium in both sexes. Serum estradiol was inversely associated with serum phosphate in both sexes to a similar degree, while serum testosterone was inversely associated with serum phosphate in both sexes with an apparent stronger effect in men than in women. Premenopausal women had lower serum phosphate compared to postmenopausal women. Serum testosterone was inversely associated with serum phosphate in postmenopausal women only. In conclusion, women > 45 years have higher serum calcium and phosphate concentrations compared to men of similar age, not explained by vitamin D or alkaline phosphatase concentrations. Serum estradiol but not testosterone was inversely associated with serum calcium while serum testosterone was inversely associated with serum phosphate in both sexes. Serum testosterone may in part explain sex differences in serum phosphate while estradiol could partly explain sex differences in serum calcium.

Genetic Evidence for a Causal Role of Serum Phosphate in Coronary Artery Calcification: The Rotterdam Study.

Background Hyperphosphatemia has been associated with coronary artery calcification (CAC) mostly in chronic kidney disease, but the association between phosphate levels within the normal phosphate range and CAC is unclear. Our objectives were to evaluate associations between phosphate levels and CAC among men and women from the general population and assess causality through Mendelian randomization. Methods and Results CAC, measured by electron-beam computed tomography, and serum phosphate levels were assessed in 1889 individuals from the RS (Rotterdam Study). Phenotypic associations were tested through linear models adjusted for age, body mass index, blood pressure, smoking, prevalent cardiovascular disease and diabetes, 25-hydroxyvitamin D, total calcium, C-reactive protein, glucose, and total cholesterol : high-density lipoprotein cholesterol ratio. Mendelian randomization was implemented through an allele score including 8 phosphate-related single-nucleotide polymorphisms. In phenotypic analyses, serum phosphate (per 1 SD) was associated with CAC with evidence for sex interaction (Pinteraction=0.003) (men ß, 0.44 [95% CI, 0.30-0.59]; P=3×10-9; n=878; women ß, 0.24 [95% CI, 0.08-0.40]; P=0.003; n=1011). Exclusion of hyperphosphatemia, chronic kidney disease (estimated glomerular filtration rate <60 mL/min per 1.73 m2) and prevalent cardiovascular disease yielded similar results. In Mendelian randomization analyses, instrumented phosphate was associated with CAC (total population ß, 0.93 [95% CI: 0.07-1.79]; P=0.034; n=1693), even after exclusion of hyperphosphatemia, chronic kidney disease and prevalent cardiovascular disease (total population ß, 1.23 [95% CI, 0.17-2.28]; P=0.023; n=1224). Conclusions Serum phosphate was associated with CAC in the general population with stronger effects in men. Mendelian randomization findings support a causal relation, also for serum phosphate and CAC in subjects without hyperphosphatemia, chronic kidney disease, and cardiovascular disease. Further research into underlying mechanisms of this association and sex differences is needed.

Disentangling the genetics of lean mass.

Background: Lean body mass (LM) plays an important role in mobility and metabolic function. We previously identified five loci associated with LM adjusted for fat mass in kilograms. Such an adjustment may reduce the power to identify genetic signals having an association with both lean mass and fat mass. Objectives: To determine the impact of different fat mass adjustments on genetic architecture of LM and identify additional LM loci. Methods: We performed genome-wide association analyses for whole-body LM (20 cohorts of European ancestry with n = 38,292) measured using dual-energy X-ray absorptiometry) or bioelectrical impedance analysis, adjusted for sex, age, age2, and height with or without fat mass adjustments (Model 1 no fat adjustment; Model 2 adjustment for fat mass as a percentage of body mass; Model 3 adjustment for fat mass in kilograms). Results: Seven single-nucleotide polymorphisms (SNPs) in separate loci, including one novel LM locus (TNRC6B), were successfully replicated in an additional 47,227 individuals from 29 cohorts. Based on the strengths of the associations in Model 1 vs Model 3, we divided the LM loci into those with an effect on both lean mass and fat mass in the same direction and refer to those as "sumo wrestler" loci (FTO and MC4R). In contrast, loci with an impact specifically on LM were termed "body builder" loci (VCAN and ADAMTSL3). Using existing available genome-wide association study databases, LM increasing alleles of SNPs in sumo wrestler loci were associated with an adverse metabolic profile, whereas LM increasing alleles of SNPs in "body builder" loci were associated with metabolic protection. Conclusions: In conclusion, we identified one novel LM locus (TNRC6B). Our results suggest that a genetically determined increase in lean mass might exert either harmful or protective effects on metabolic traits, depending on its relation to fat mass.

Serum Phosphate Is Associated With Fracture Risk: The Rotterdam Study and MrOS.

Extreme phosphate levels (P) have been associated with mineralization defects and increased fracture risk. Whether P within normal range is related to bone health in the general population is not well understood. To investigate the association of P with bone mineral density (BMD) and fracture risk, we assessed two population-based cohorts: the Dutch Rotterdam Study (RS-I, RS-II, RS-III; n = 6791) and the US Osteoporotic Fractures in Men (MrOS; n = 5425) study. The relationship of P with lumbar spine (LS) and femoral neck (FN) BMD was tested in all cohorts via linear models; fracture risk was tested in RS-I, RS-II, and MrOS through Cox models, after follow-up of 8.6, 6.6, and 10.9 years, respectively. Adjustments were made for age, body mass index, smoking, serum levels of calcium, potassium, 25-hydroxyvitamin D, estimated glomerular filtration rate (eGFR), FN-BMD, prevalent diabetes, and cardiovascular disease. Additional adjustments were made for phosphate intake, parathyroid hormone, and fibroblast growth factor 23 levels in MrOS. We further stratified by eGFR. Results were pooled through study-level meta-analyses. Hazard ratios (HR) and betas (ß) (from meta-analyses) are expressed per 1 mg/dL P increase. P was positively associated with fracture risk in men and women from RS, and findings were replicated in MrOS (pooled HR all [95% CI]: 1.47 [1.31-1.65]). P was associated with fracture risk in subjects without chronic kidney disease (CKD): all (1.44 [1.26-1.63]) and in men with CKD (1.93 [1.42-2.62]). P was inversely related to LS-BMD in men (ß: -0.06 [-0.11 to -0.02]) and not to FN-BMD in either sex. In summary, serum P was positively related to fracture risk independently from BMD and phosphate intake after adjustments for potential confounders. P and LS-BMD were negatively related in men. Our findings suggest that increased P levels even within normal range might be deleterious for bone health in the normal population. © 2017 American Society for Bone and Mineral Research.

Bone health and coronary artery calcification: The Rotterdam Study.

OBJECTIVES: Vascular calcification has been associated inconsistently to low bone mineral density and fractures. The aims of the present study were to investigate the associations between coronary artery calcification (CAC) and BMD change, BMD and fracture risk in elderly subjects of the population-based Rotterdam Study. METHODS: BMD was assessed through dual-energy X-ray absorptiometry and CAC through Electron-Beam Computed Tomography in 582 men and 694 women. We investigated the associations between BMD change (6.4 years follow-up) and CAC at follow-up and between BMD and CAC (measured simultaneously). In sensitivity analyses we stratified analyses for estradiol levels in women. The association between CAC and fracture risk (9 years follow-up) was tested through competing-risks models. Models were sex-stratified and adjusted for age, body mass index, smoking, bisphosphonate use and age at menopause. RESULTS: There was no association between BMD change and CAC in men. In women, each 1% increase in annual BMD loss was significantly associated with higher follow-up CAC [ß = 0.22 (0.06-0.38), p=0.006; prevalence ratio: 4%]. Stratified analyses showed significant associations between BMD loss and follow-up CAC only in women with lower estradiol levels. We found no association between CAC and fracture risk and no association between BMD and CAC cross-sectionally. CONCLUSIONS: BMD loss was associated with higher follow-up CAC in women, which might be related to low estrogen levels. No association between CAC and BMD or fracture risk was found. Further studies are required to elucidate the mechanisms that might underlie the association between BMD change and coronary calcification in women.

Osteoporotic vertebral fractures during pregnancy: be aware of a potential underlying genetic cause.

CONTEXT: Although the baby growing in its mother's womb needs calcium for skeletal development, osteoporosis and fractures very rarely occur during pregnancy. CASE PRESENTATION: A 27-year-old woman in the seventh month of her first pregnancy contracted midthoracic back pain after lifting an object. The pain was attributed to her pregnancy, but it remained postpartum. Her past medical history was uneventful, except for severely reduced vision of her left eye since birth. Family history revealed that her maternal grandmother had postmenopausal osteoporosis and her half-brother had three fractures during childhood after minor trauma. Her height was 1.58 m; she had no blue sclerae or joint hyperlaxity. Laboratory examination including serum calcium, phosphate, alkaline phosphatase, creatinine, ß-carboxyterminal cross-linking telopeptide of type I collagen, 25-hydroxyvitamin D, and TSH was normal. Multiple thoracic vertebral fractures were diagnosed on x-ray examination, and dual-energy x-ray absorptiometry scanning showed severe osteoporosis (Z-scores: L2-L4, -5.6 SD; femur neck, -3.9 SD). DNA analyses revealed two compound heterozygous missense mutations in LRP5. The patient's mother carried one of the LRP5 mutations and was diagnosed with osteoporosis. Her half-brother, treated with cabergoline for a microprolactinoma, also had osteoporosis of the lumbar spine on dual-energy x-ray absorptiometry and carried the same LRP5 mutation. The patient was treated with risedronate for 2.5 years. Bone mineral density and back pain improved. She stopped bisphosphonate use 6 months before planning a second pregnancy. CONCLUSION: Our patient was diagnosed with osteoporosis pseudoglioma syndrome/familial exudative vitreoretinopathy. Potential underlying genetic causes should be considered in pregnancy-associated osteoporosis with implications for patients and relatives. More studies regarding osteoporosis treatment preceding conception are desirable.

Bone mineral density and chronic lung disease mortality: the rotterdam study.

CONTEXT: Low bone mineral density (BMD) has been associated with increased all-cause mortality. Cause-specific mortality studies have been controversial. OBJECTIVE: The aim of the study was to investigate associations between BMD and all-cause mortality and in-depth cause-specific mortality. DESIGN AND SETTING: We studied two cohorts from the prospective Rotterdam Study (RS), initiated in 1990 (RS-I) and 2000 (RS-II) with average follow-up of 17.1 (RS-I) and 10.2 (RS-II) years until January 2011. Baseline femoral neck BMD was analyzed in SD values. Deaths were classified according to International Classification of Diseases into seven groups: cardiovascular diseases, cancer, infections, external, dementia, chronic lung diseases, and other causes. Gender-stratified Cox and competing-risks models were adjusted for age, body mass index, and smoking. PARTICIPANTS: The study included 5779 subjects from RS-I and 2055 from RS-II. MAIN OUTCOME MEASUREMENTS: We measured all-cause and cause-specific mortality. RESULTS: A significant inverse association between BMD and all-cause mortality was found in males [expressed as hazard ratio (95% confidence interval)]: RS-I, 1.07 (1.01-1.13), P = .020; RS-II, 1.31 (1.12-1.55), P = .001); but it was not found in females: RS-I, 1.05 (0.99-1.11), P = .098; RS-II, 0.91 (0.74-1.12), P = .362. An inverse association with chronic lung disease mortality was found in males [RS-I, 1.75 (1.34-2.29), P < .001; RS-II, 2.15 (1.05-4.42), P = .037] and in RS-I in females [1.72 (1.16-2.57); P = .008], persisting after multiple adjustments and excluding prevalent chronic obstructive pulmonary disease. A positive association between BMD and cancer mortality was detected in females in RS-I [0.89 (0.80-0.99); P = .043]. No association was found with cardiovascular mortality. CONCLUSIONS: BMD is inversely associated with mortality. The strong association of BMD with chronic lung disease mortality is a novel finding that needs further analysis to clarify underlying mechanisms.