Improving the vitamin D status of vitamin D deficient adults is associated with improved mitochondrial oxidative function in skeletal muscle

Evaluation of Nutrition and Performance Parameters in Division 1 Collegiate Athletes

BACKGROUND

Testing and evaluating athletes is necessary and should include performance, body composition, and nutrition. The purpose of this study was to report assessments of dietary intake, V˙O2max, and body composition in D1 collegiate athletes and examine relationships between these assessments.

METHODS

Dietary intake was assessed with 3-day recalls and compared to recommendations, and body composition was assessed via bioelectrical impedance analysis (BIA) (n = 48). V˙O2max was evaluated using a graded exercise test (GXT) with a verification bout (n = 35). Reliability between "true" V˙O2max and verification was determined. Correlations and regressions were performed.

RESULTS

Energy, carbohydrate, and micronutrient intake was lower than recommendations. Mean V˙O2max was 47.3 and 47.4 mL·kg-1·min-1 for GXT and verification, respectively. While correlations were apparent among dietary intake, V˙O2max, and body composition, percent fat-free mass (%FFM) predicted 36% of V˙O2max.

CONCLUSIONS

Collegiate athletes are not meeting energy and carbohydrate recommendations and exceed fat recommendations. Vitamin D and magnesium were low in all sports, and iron and calcium were low in females. V˙O2max ranged from 35.6 to 63.0 mL·kg-1·min-1, with females below average and males meeting typical values for their designated sport. Assessing D1 athletes can provide guidance for sports dietitians, coaches, and strength and conditioning specialists to track and monitor nutrition in athletes.

Mini-encyclopedia of mitochondria-relevant nutraceuticals protecting health in primary and secondary care-clinically relevant 3PM innovation

Despite their subordination in humans, to a great extent, mitochondria maintain their independent status but tightly cooperate with the "host" on protecting the joint life quality and minimizing health risks. Under oxidative stress conditions, healthy mitochondria promptly increase mitophagy level to remove damaged "fellows" rejuvenating the mitochondrial population and sending fragments of mtDNA as SOS signals to all systems in the human body. As long as metabolic pathways are under systemic control and well-concerted together, adaptive mechanisms become triggered increasing systemic protection, activating antioxidant defense and repair machinery. Contextually, all attributes of mitochondrial patho-/physiology are instrumental for predictive medical approach and cost-effective treatments tailored to individualized patient profiles in primary (to protect vulnerable individuals again the health-to-disease transition) and secondary (to protect affected individuals again disease progression) care. Nutraceuticals are naturally occurring bioactive compounds demonstrating health-promoting, illness-preventing, and other health-related benefits. Keeping in mind health-promoting properties of nutraceuticals along with their great therapeutic potential and safety profile, there is a permanently growing demand on the application of mitochondria-relevant nutraceuticals. Application of nutraceuticals is beneficial only if meeting needs at individual level. Therefore, health risk assessment and creation of individualized patient profiles are of pivotal importance followed by adapted nutraceutical sets meeting individual needs. Based on the scientific evidence available for mitochondria-relevant nutraceuticals, this article presents examples of frequent medical conditions, which require protective measures targeted on mitochondria as a holistic approach following advanced concepts of predictive, preventive, and personalized medicine (PPPM/3PM) in primary and secondary care.

Frontiers in sarcopenia: Advancements in diagnostics, molecular mechanisms, and therapeutic strategies

The onset of sarcopenia is intimately linked with aging, posing significant implications not only for individual patient quality of life but also for the broader societal healthcare framework. Early and accurate identification of sarcopenia and a comprehensive understanding of its mechanistic underpinnings and therapeutic targets paramount to addressing this condition effectively. This review endeavors to present a cohesive overview of recent advancements in sarcopenia research and diagnosis. We initially delve into the contemporary diagnostic criteria, specifically referencing the European Working Group on Sarcopenia in Older People (EWGSOP) 2 and Asian Working Group on Sarcopenia (AWGS) 2019 benchmarks. Additionally, we elucidate comprehensive assessment techniques for muscle strength, quantity, and physical performance, highlighting tools such as grip strength, chair stand test, dual-energy X-ray Absorptiometry (DEXA), bioelectrical impedance analysis (BIA), gait speed, and short physical performance battery (SPPB), while also discussing their inherent advantages and limitations. Such diagnostic advancements pave the way for early identification and unequivocal diagnosis of sarcopenia. Proceeding further, we provide a deep-dive into sarcopenia's pathogenesis, offering a thorough examination of associated signaling pathways like the Myostatin, AMP-activated protein kinase (AMPK), insulin/IGF-1 Signaling (IIS), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. Each pathway's role in sarcopenia mediation is detailed, underscoring potential therapeutic target avenues. From a mechanistic perspective, the review also underscores the pivotal role of mitochondrial dysfunction in sarcopenia, emphasizing elements such as mitochondrial oxidative overload, mitochondrial biogenesis, and mitophagy, and highlighting their therapeutic significance. At last, we capture recent strides made in sarcopenia treatment, ranging from nutritional and exercise interventions to potential pharmacological and supplementation strategies. In sum, this review meticulously synthesizes the latest scientific developments in sarcopenia, aiming to enhance diagnostic precision in clinical practice and provide comprehensive insights into refined mechanistic targets and innovative therapeutic interventions, ultimately contributing to optimized patient care and advancements in the field.

Effects of vitamin D3 supplementation on strength of lower and upper extremities in athletes: an updated systematic review and meta-analysis of randomized controlled trials

Background

Coaches and athletes are increasingly interested in understanding athletes' serum vitamin D levels, their impact on strength, physical performance, and athletic outcomes. Previous meta-analyses were reported with limited sample size and no significant overall effect was found. Hence, it is crucial to conduct a thorough and up-to-date systematic examination and meta-analysis to elucidate the potential advantages of supplementing with vitamin D3 in enhancing muscle strength for athletes.

Methods

We performed a thorough investigation, spanning three databases (PubMed, EBSCO, and Cochrane Library), seeking randomized controlled trials (RCTs) in all languages. These trials delved into the influence of vitamin D3 supplementation on the changes of pre- and post-intervention muscle strength in healthy athletes. Our systematic examination and meta-analysis took into account serum 25(OH)D levels exceeding 30 ng/mL as a marker of adequacy.

Results

Ten RCTs, comprising 354 athletes (185 in the vitamin D3 group and 169 in the placebo group), fulfilled the inclusion criteria. During the study, 36 athletes were lost to follow-up, leaving 318 athletes (166 in the vitamin D3 group and 152 in the placebo group) with documented complete results. In comparison with the placebo group, there is a significant increase between the changes of pre- and post-intervention serum 25(OH)D levels among athletes following a period of vitamin D3 supplementation (MD 14.76, 95% CI: 8.74 to 20.77, p < 0.0001). Overall effect of four strength measurements including handgrip, one repetition maximum Bench Press (1-RM BP), vertical jump, and quadriceps contraction was not significantly improved (SMD 0.18, 95% CI: -0.02 to 0.37, p = 0.08), but there was a significant increase in quadriceps contraction (SMD 0.57, 95% CI: 0.04 to 1.11, p = 0.04).

Conclusion

This updated meta-analysis indicates the potential benefits of vitamin D supplementation for enhancing muscle strength in athletes when analyzing its quantitatively synthesized effects. With limited available studies for the quantitative synthesis, it cannot warrant significant overall enhancements in muscle strength when athletes attain adequate serum 25(OH)D levels through supplementation.

Nutritional approaches targeting mitochondria for the prevention of sarcopenia

A decline in function and loss of mass, a condition known as sarcopenia, is observed in the skeletal muscles with aging. Sarcopenia has a negative effect on the quality of life of elderly. Individuals with sarcopenia are at particular risk for adverse outcomes, such as reduced mobility, fall-related injuries, and type 2 diabetes mellitus. Although the pathogenesis of sarcopenia is multifaceted, mitochondrial dysfunction is regarded as a major contributor for muscle aging. Hence, the development of preventive and therapeutic strategies to improve mitochondrial function during aging is imperative for sarcopenia treatment. However, effective and specific drugs that can be used for the treatment are not yet approved. Instead studies on the relationship between food intake and muscle aging have suggested that nutritional intake or dietary control could be an alternative approach for the amelioration of muscle aging. This narrative review approaches various nutritional components and diets as a treatment for sarcopenia by modulating mitochondrial homeostasis and improving mitochondria. Age-related changes in mitochondrial function and the molecular mechanisms that help improve mitochondrial homeostasis are discussed, and the nutritional components and diet that modulate these molecular mechanisms are addressed.

Neuroprotective effects of vitamin D in an Alzheimer's disease rat model: Improvement of mitochondrial dysfunction via calcium/calmodulin-dependent protein kinase kinase 2 activation of Sirtuin1 phosphorylation

Mitochondrial dysfunction is an early event in Alzheimer's disease (AD) pathogenesis. To assess the impact of vitamin D3 (Vit.D) on neurogenesis, we investigated its role in mitigating cognitive impairment and mitochondrial dysfunction through calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2)-mediated phosphorylation of Sirtuin1 (SIRT1) in an aluminum-chloride-D-galactose (AlCl3-D-gal)-induced AD rat model. Rats were distributed into four groups: control, AlCl3 + D-gal (10 + 60 mg/kg, ip), Vit.D (500 IU/kg, po), and AlCl3 + D-gal+Vit.D. Novel object recognition (NOR), Morris Water Maze, and passive avoidance (PA) tests were used to measure memory abilities. The hippocampal tissue was used to assess vitamin D3 receptor (VDR) and peroxisome-proliferator-activated-receptor-γ-coactivator-1α (PGC-1α) expression by quantitative real-time polymerase chain reaction (qRT-PCR), CAMKK2, p-SIRT1, phosphorylated-AMP-activated protein kinase (p-AMPK), dynamin-related-protein-1 (Drp1), and mitofusin-1 (Mnf1) proteins by western blot and Ca2+ levels, endothelial nitic oxide synthase (eNOS), superoxide dismutase (SOD), amyloid beta (Aβ), and phospho tau (p-Tau) via enzyme-linked immunosorbent assay(ELISA) in addition to histological and ultrastructural examination of rat's brain tissue. Vit.D-attenuated hippocampal injury reversed the cognitive decline and Aβ aggregation, and elevated p-Tau levels in the AlCl3 + D-gal-induced AD rat model. In AlCl3 + D-gal-exposed rats, Vit.D induced VDR expression, normalized Ca2+ levels, elevated CAMKK2, p-AMPK, p-SIRT1, and PGC-1α expression. Vit.D reduced Drp1, induced Mnf1, increased mitochondrial membrane potential, preserved mitochondrial structure, restored normal mitochondrial function, and retained normal eNOS level and SOD activity in AlCl3 + D-gal rats. In conclusion, our findings proved that Vit.D may ameliorate cognitive deficits in AlCl3 + D-gal-induced AD by restoring normal mitochondrial function and reducing inflammatory and oxidative stress via CAMKK2-AMPK/SIRT1 pathway upregulation.

Optimal serum 25-hydroxyvitamin D level to prevent sarcopenia in patients with heart failure: Insights from a dose-response relationship

BACKGROUND AND AIMS

Low serum 25-hydroxyvitamin D (25 [OH]D) levels have been associated with sarcopenia, frailty, and risk of cardiovascular disease, whereas high levels negatively impact clinical outcomes. We determined optimal serum 25(OH)D concentrations to minimise the probability of sarcopenia in patients with heart failure (HF) by examining the dose-dependent relationship between serum 25(OH)D levels and sarcopenia.

METHODS AND RESULTS

We enrolled 461 consecutive patients with HF (mean age, 72 ± 15 years; 39% female) who underwent dual-energy X-ray absorptiometry. Serum 25(OH)D levels were measured using a chemiluminescence immunoassay. Sarcopenia was diagnosed according to the 2019 Asian Working Group for Sarcopenia criteria. Overall, 49% of enrolled patients were diagnosed with sarcopenia. Adjusted logistic regression with restricted cubic spline function revealed that the odds ratio (OR) of sarcopenia increased in patients with HF presenting serum 25(OH)D levels <14.6 ng/ml or > 31.4 ng/ml, reaching the lowest OR at ∼20 ng/ml. Multivariate logistic regression revealed that a serum 25(OH)D level below 14.6 ng/mL was independently associated with the presence of sarcopenia (adjusted OR: 2.16, 95% confidence interval [CI]: 1.24-3.78). Incorporating serum 25(OH)D levels <14.6 ng/ml, but not <20.0 ng/ml, in the baseline model improved continuous net reclassification (0.334, 95% CI: 0.122-0.546) in patients with HF.

CONCLUSION

A U-shaped relationship exists between serum 25(OH)D levels and sarcopenia probability in patients with HF. Maintaining serum 25(OH)D levels between 14.6 and 31.4 ng/ml may help prevent sarcopenia in patients with HF.

Lack of vitamin D signalling shifts skeletal muscles towards oxidative metabolism

BACKGROUND

Mice lacking vitamin D receptor (VDR) exhibit a glycogen storage disorder, disrupting carbohydrate utilization in muscle. Here, we asked if the defective carbohydrate metabolism alters the fat utilization by the skeletal muscles of vdr-/- mice.

METHODS

To check the effect of high-fat-containing diets on muscle mass and metabolism of vdr-/- mice, we subjected them to two different milk fat-based diets (milk fat diet with 60% of energy from milk fat and milk-based diet [MBD] with 37% of energy from milk fat) and lard-based high-fat diet (HFD) containing 60% of energy from lard fat. Skeletal muscles and pancreas from these mice were analysed using RNA sequencing, quantitative reverse transcription polymerase chain reaction and western blot to understand the changes in signalling and metabolic pathways. Microscopic analyses of cryosections stained with haematoxylin and eosin, BODIPY, succinate dehydrogenase and periodic acid-Schiff reagent were performed to understand changes in morphology and metabolism of muscle fibres and pancreatic islets.

RESULTS

Transcriptomic analyses showed that the skeletal muscles of vdr-/- mice exhibit upregulation of the fatty acid oxidation pathways, suggesting a shift towards increased lipid utilization even in a carbohydrate-enriched regular chow diet (chow). Two different milk fat-enriched diets restored body weight (12.01 ± 0.33 g in chow vs. 17.99 ± 0.62 g in MBD) and muscle weights (38.58 ± 3.84 mg in chow vs. 110.72 ± 1.96 mg in MBD for gastrocnemius [GAS]) of vdr-/- mice. Muscle ATP levels (0.56 ± 0.18 μmol in chow vs. 1.48 ± 0.08 μmol in MBD) and protein synthesis (0.25 ± 0.04 A.U. in chow vs. 2.02 ± 0.06 A.U. in MBD) were upregulated by MBD. However, despite increasing muscle energy levels, HFD failed to restore the muscle mass and cross-sectional area to that of wild-type (WT) mice (104.95 ± 2.6 mg for WT mice on chow vs. 77.26 ± 1.7 mg for vdr-/- mice on HFD for GAS). Moreover, HFD disrupted glucose homeostasis in vdr-/- mice, while MBD restored it. We further analysed insulin response and pancreatic insulin levels of these mice to show that HFD led to reduced insulin levels in pancreatic beta cells of vdr-/- mice (mean intensity of 1.5 × 10-8 for WT mice on chow vs. 4.3 × 10-9 for vdr-/- mice on HFD). At the same time, MBD restored glucose-stimulated pancreatic insulin response (mean intensity of 9.2 × 10-9 ).

CONCLUSIONS

Skeletal muscles of vdr-/- mice are predisposed to utilize fatty acids as their primary energy source to circumvent their defective carbohydrate utilization. Thus, HFDs could restore energy levels in the skeletal muscles of vdr-/- mice. This study reveals that when mice are subjected to a lard-based HFD, VDR signalling is essential for maintaining insulin levels in pancreatic islets. Our data show a critical role of VDR in muscle metabolic flexibility and pancreatic insulin response.

Epimeric vitamin D and cardiovascular structure and function in advanced CKD and after kidney transplantation

BACKGROUND

25-hydroxyvitamin D can undergo C-3 epimerization to produce 3-epi-25(OH)D3. 3-epi-25(OH)D3 levels decline in chronic kidney disease (CKD), but its role in regulating the cardiovascular system is unknown. Herein, we examined the relationship between 3-epi-25(OH)D3, and cardiovascular functional and structural endpoints in patients with CKD.

METHODS

We examined n = 165 patients with advanced CKD from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) study cohort, including those who underwent kidney transplant (KTR, n = 76) and waitlisted patients who did not (NTWC, n = 89). All patients underwent cardiopulmonary exercise testing and echocardiography at baseline, 2 months and 12 months. Serum 3-epi-25(OH)D3 was analyzed by liquid chromatography-tandem mass spectrometry.

RESULTS

Patients were stratified into quartiles of baseline 3-epi-25(OH)D3 (Q1: <0.4 ng/mL, n = 51; Q2: 0.4 ng/mL, n = 26; Q3: 0.5-0.7 ng/mL, n = 47; Q4: ≥0.8 ng/mL, n = 41). Patients in Q1 exhibited lower peak oxygen uptake [VO2Peak = 18.4 (16.2-20.8) mL/min/kg] compared with Q4 [20.8 (18.6-23.2) mL/min/kg; P = .009]. Linear mixed regression model showed that 3-epi-25(OH)D3 levels increased in KTR [from 0.47 (0.30) ng/mL to 0.90 (0.45) ng/mL] and declined in NTWC [from 0.61 (0.32) ng/mL to 0.45 (0.29) ng/mL; P < .001]. Serum 3-epi-25(OH)D3 was associated with VO2Peak longitudinally in both groups [KTR: β (standard error) = 2.53 (0.56), P < .001; NTWC: 2.73 (0.70), P < .001], but was not with left ventricular mass or arterial stiffness. Non-epimeric 25(OH)D3, 24,25(OH)2D3 and the 25(OH)D3:24,25(OH)2D3 ratio were not associated with any cardiovascular outcome (all P > .05).

CONCLUSIONS

Changes in 3-epi-25(OH)D3 levels may regulate cardiovascular functional capacity in patients with advanced CKD.

Physiological Evidence and Therapeutic Outcomes of Vitamin D on Cardiovascular Diseases

Vitamin D hormone is an important regulator of various physiological functions, and its deficiency is characterized by an imbalance in parathyroid hormone and calcium homeostasis. The role of vitamin D in cardiovascular physiology is well demonstrated in animal and humanbased studies. In this context, hyperlipidemia, increased atherogenic plaques, cardiac inflammation, hypertension, myocarditis, myocardial infarction, and heart failure are some of the commonest known conditions connected with vitamin D deficiency. Supplementation of vitamin D is recommended to achieve normal serum vitamin D concentrations, nonetheless, in clinical trials often seen discrepancies concerning the supplementation effects and effectiveness. This review summarizes the data on the role of vitamin D in cardiovascular health along with some recent clinical findings regarding the effects of vitamin D supplementation.

The Effect of Vitamin D Consumption on Pro-Inflammatory Cytokines in Athletes: A Systematic Review of Randomized Controlled Trials

Vitamin D is essential for the optimal health of the skeletal system. However, this vitamin also plays a role in other functions of the human body, such as muscle, immune, and inflammatory functions. Some studies have reported that adequate levels of vitamin D improve immune system function by reducing the levels of certain pro-inflammatory cytokines, which can protect against the risk of post-exercise illness. This systematic review aims to investigate the effects of vitamin D supplementation on pro-inflammatory cytokines in athletes. This study was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A literature search was conducted in SPORTDiscus, PubMed, ScienceDirect, and Google Scholar up to 1 October 2023. The quality of the articles was evaluated using the Risk of Bias 2 Tool. After searching the databases, a total of 7417 studies were identified, 6 of which met the eligibility criteria, and their outcomes were presented. The six studies included 176 participants. All six studies are randomized control trials, including a total of 176 subjects, primarily men (81%). Regarding the types of athletes, most participants were endurance athletes. Our investigation in this systematic review demonstrated that out of the six studies, only two of them reported significant changes in IL-6 and TNF-α levels after taking high-dose vitamin D. Other studies did not present any significant changes after vitamin D supplementation in athletes with respect to IL-6 and TNF-α levels. Further studies are needed to determine the effectiveness of vitamin D supplementation for athletes as a disease-prone community.

Vitamin D and Its Role on the Fatigue Mitigation: A Narrative Review

Vitamin D has historically been associated with bone metabolism. However, over the years, a growing body of evidence has emerged indicating its involvement in various physiological processes that may influence the onset of numerous pathologies (cardiovascular and neurodegenerative diseases, rheumatological diseases, fertility, cancer, diabetes, or a condition of fatigue). This narrative review investigates the current knowledge of the pathophysiological mechanisms underlying fatigue and the ways in which vitamin D is implicated in these processes. Scientific studies in the databases of PubMed, Scopus, and Web of Science were reviewed with a focus on factors that play a role in the genesis of fatigue, where the influence of vitamin D has been clearly demonstrated. The pathogenic factors of fatigue influenced by vitamin D are related to biochemical factors connected to oxidative stress and inflammatory cytokines. A role in the control of the neurotransmitters dopamine and serotonin has also been demonstrated: an imbalance in the relationship between these two neurotransmitters is linked to the genesis of fatigue. Furthermore, vitamin D is implicated in the control of voltage-gated calcium and chloride channels. Although it has been demonstrated that hypovitaminosis D is associated with numerous pathological conditions, current data on the outcomes of correcting hypovitaminosis D are conflicting. This suggests that, despite the significant involvement of vitamin D in regulating mechanisms governing fatigue, other factors could also play a role.

Effect of vitamin D3 supplementation in winter on physical performance of university students: a one-month randomized controlled trial

BACKGROUND

There is epidemiological evidence which suggests an association between 25-hydroxyvitamin D [25(OH)D] levels and bone and muscle function; however, it is unclear whether vitamin D supplementation has an added benefit beyond bone health. Here, we investigated the effects of vitamin D3 supplementation (1 month) on physical performance in Chinese university students in winter.

METHODS

One hundred and seventeen eligible subjects with 25(OH)D (19.2 ± 7.8 ng/mL) were randomly assigned to either vitamin D3 supplement (N = 56; 1000 IU/day) or the control (N = 61) group for 1 month. Pre- and post-measurements included: 1) serum levels of 25(OH)D; 2) musculoskeletal and pulmonary function [vertical jump height (VJH) and right handgrip strength (RHS), forced vital capacity (FVC), and forced expiratory volume at 1s (FEV1)]; 3) bone turnover markers [parathyroid hormone (PTH), n-terminal osteocalcin (N-MID), and calcium]; 4) hemoglobin-related parameters [hemoglobin (Hb), hematocrit (HCT), red blood cells (RBC), and red cell distribution width (RDW)]; 5) lipid parameters [total triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)]; 6) Fatigue-related indicators [serum creatine kinase (CK), lactate dehydrogenase (LDH), and total testosterone (T)]. In addition, aerobic capacity was assessed by measuring maximal oxygen uptake (VO2max) at baseline.

RESULTS

During wintertime, supplementation with 1000 IU/d of vitamin D3 significantly increased serum 25(OH)D levels (from 18.85 ± 7.04 to 26.98 ± 5.88 ng/mL, p < 0.05), accompanied by a decrease of PTH (p < 0.05). However, vitamin D3 supplementation did not significantly impact the physical performance, serum lipid parameters, and bone turnover markers of students. Furthermore, 25(OH)D was found to be positively correlated with VJH and negatively correlated with PTH and TC at the beginning and end of the study (p < 0.05). In addition, the multiple linear regression analysis showed that 25(OH)D combined with athletic, gender, height, weight, Hb, and FVC could account for 84.0% of the VO2max value.

CONCLUSIONS

The study demonstrated that one-month of 1000 IU/d of vitamin D3 supplementation during the winter had beneficial effects on 25(OH)D status and PTH. However, vitamin D3 intervention was not sufficient to improve physical performance. Furthermore, 25(OH)D levels combined with athletic, Hb and FVC could be a predictor of VO2max.

Vitamin D3 Exerts Beneficial Effects on C2C12 Myotubes through Activation of the Vitamin D Receptor (VDR)/Sirtuins (SIRT)1/3 Axis

The onset of sarcopenia is associated with a decline in vitamin D receptor (VDR) expression, wherein reduced VDR levels contribute to muscle atrophy, while heightened expression promotes muscle hypertrophy. Like VDR, the age-related decline in protein deacetylase sirtuin (SIRT) expression is linked to the development of sarcopenia and age-related muscle dysfunction. This study aimed to investigate whether the VDR agonist 1,25-dihydroxyvitamin D3 (1,25VD3) exerts beneficial effects on muscles through interactions with sirtuins and, if so, the underlying molecular mechanisms. Treatment of 1,25VD3 in differentiating C2C12 myotubes substantially elevated VDR, SIRT1, and SIRT3 expression, enhancing their differentiation. Furthermore, 1,25VD3 significantly enhanced the expression of key myogenic markers, including myosin heavy chain (MyHC) proteins, MyoD, and MyoG, and increased the phosphorylation of AMPK and AKT. Conversely, VDR knockdown resulted in myotube atrophy and reduced SIRT1 and SIRT3 levels. In a muscle-wasting model triggered by IFN-γ/TNF-α in C2C12 myotubes, diminished VDR, SIRT1, and SIRT3 levels led to skeletal muscle atrophy and apoptosis. 1,25VD3 downregulated the increased expression of muscle atrophy-associated proteins, including FoxO3a, MAFbx, and MuRF1 in an IFN-γ/TNF-α induced atrophy model. Importantly, IFN-γ/TNF-α significantly reduced the mtDNA copy number in the C2C12 myotube, whereas the presence of 1,25VD3 effectively prevented this decrease. These results support that 1,25VD3 could serve as a potential preventive or therapeutic agent against age-related muscle atrophy by enhancing the VDR/SIRT1/SIRT3 axis.

Improved Healing of Diabetic Foot Ulcers After High-dose Vitamin D: A Randomized Double-blinded Clinical Trial

Background. Chronic foot ulcers are a major cause of morbidity in people with diabetes with a lifetime risk of 25%. Treatment is challenging and the recurrence rates of foot ulcers are >50% after 3 years. Vitamin D deficiency is more common in people with diabetes with chronic foot ulcers, compared to both people without diabetes as well as people with diabetes but without foot ulcers. Purpose/aim of study. To assess the efficacy of high-dose compared to low-dose Cholecalciferol vitamin D3 on healing of chronic diabetic foot ulcers. Materials and methods. We included people with diabetes with one or more foot ulcers lasting for more than 6 weeks. Patients were randomly allocated to either a daily oral intake of high-dose (170 μg) or low-dose (20 μg) vitamin D3 (Cholecalciferol). We saw patients in the outpatient clinic after 4, 12, 24, 36, and 48 weeks. At each visit, we measured the ulcer with a specialized camera, and associated software and the area (cm2) was calculated. Patients and assessors were blinded to treatment allocation. We followed all patients for 48 weeks or until wound healing or surgical treatment. Findings/results. We included 48 patients in the analysis (24 in each group), with a total of 64 ulcers. Among them 41 ulcers were followed until healing or 48-week follow-up and 20 ulcers were surgically treated during the study period. Three patients were lost for follow-up. The intention-to-treat analysis showed a significantly higher rate of ulcer healing in the high-dose group with 21 of 30 (70%) healed ulcers compared to 12 of 34 (35%) in the low-dose group (P = .012). Median ulcer reduction at final follow-up was 100% (interquartile range [IQR]: 72-100) in the high-dose group and 57% (IQR: -28 to 100) in the low-dose group. Furthermore, we found a significant effect of high-dose vitamin D on ulcer reduction in the repeated measures analysis of variance. Conclusions. We found high-dose vitamin D3 to be efficient, compared to low-dose vitamin D3, in promoting healing in chronic diabetic foot ulcers.

Adverse effect propensity: A new feature of Gulf War illness predicted by environmental exposures

A third of 1990-1 Gulf-deployed personnel developed drug/chemical-induced multisymptom illness, "Gulf War illness" (GWI). Veterans with GWI (VGWI) report increased drug/exposure adverse effects (AEs). Using previously collected data from a case-control study, we evaluated whether the fraction of exposures that engendered AEs ("AE Propensity") is increased in VGWI (it was); whether AE Propensity is related to self-rated "chemical sensitivity" (it did); and whether specific exposures "predicted" AE Propensity (they did). Pesticides and radiation exposure were significant predictors, with copper significantly "protective"-in the total sample (adjusted for GWI-status) and separately in VGWI and controls, on multivariable regression. Mitochondrial impairment and oxidative stress (OS) underlie AEs from many exposures irrespective of nominal specific mechanism. We hypothesize that mitochondrial toxicity and interrelated OS from pesticides and radiation position people on the steep part of the curve of mitochondrial impairment and OS versus symptom/biological disruption, amplifying impact of new exposures. Copper, meanwhile, is involved in critical OS detoxification processes.

1,25-Dihydroxyvitamin D3 alleviates hyperandrogen-induced ferroptosis in KGN cells

PURPOSE

Hyperandrogenism, one of the most frequent causes of anovulation in women, increases the risk of metabolic disorders in patients with polycystic ovary syndrome (PCOS). Ferroptosis, characterized by iron-dependent lipid peroxidation, has provided new insight into the progression of PCOS. 1,25-dihydroxyvitamin D3 (1,25D3) may play a role in reproduction because its receptor, VDR, which contributes to the inhibition of oxidative stress, is primarily located in the nuclei of granulosa cells. This study has therefore investigated whether 1,25D3 and hyperandrogenism affect granulosa-like tumor cells (KGN cells) through ferroptosis.

METHODS

KGN cells were treated with dehydroepiandrosterone (DHEA) or pretreated with 1,25D3. Cell viability was evaluated with the cell counting kit-8 (CCK-8) assay. The mRNA and protein expression levels of ferroptosis-related molecules, including glutathione peroxidase 4 (GPX4), solute carrier family 7 member (SLC7A11), and long-chain acyl-CoA synthetase 4 (ACSL4), were assessed via qRT-PCR and western blot. The concentration of malondialdehyde (MDA) was measured by ELISA. The rates of reactive oxygen species (ROS) production and lipid peroxidation were assessed via photometric methods.

RESULTS

Decreased cell viability, suppression of GPX4 and SLC7A11 expression, increased expression of ACSL4, elevated levels of MDA, accumulation of ROS, and increased lipid peroxidation, which are changes representative of ferroptosis, were observed in KGN cells after treatment with DHEA. Pretreatment with 1,25D3 in KGN cells significantly prevented these changes.

CONCLUSIONS

Our findings demonstrate that 1,25D3 attenuates hyperandrogen-induced ferroptosis of KGN cells. This finding might lead to new insights into the pathophysiology and therapy of PCOS and provides new evidence for the treatment of PCOS with 1,25D3.

The Association Between Vitamin D Level and Chest Pain, Anxiety, and Fatigue in Patients With Coronary Artery Disease

This study sought to assess the association between vitamin D deficiency (VDD) and chest pain, anxiety, and fatigue in patients with coronary artery disease (CAD). A cross-sectional study was conducted to collect data from a sample of 90 participants with CAD. Serum 25OHD3 was measured using a radioimmunoassay procedure. Chest pain was assessed using the Numeric Pain Rating Scale, anxiety using the Anxiety Subscale, and fatigue by the General Fatigue subscale. The majority of participants (80%) had VDD. Results showed that the level of vitamin D was significantly negatively associated with chest pain (r = -.43, p = .00); anxiety (r = -.466, p = .00); and fatigue (r = -.25, p = .018). Findings suggest the role of VDD in heightened central sensitivity in cardiac-related symptoms such as chest pain, anxiety, and fatigue. Patients with CAD should be monitored for VDD so that the condition can be corrected.

Vitamin D Receptor Mediates Attenuating Effect of Lithocholic Acid on Dextran Sulfate Sodium Induced Colitis in Mice

Bile acids are major components of bile; they emulsify dietary lipids for efficient digestion and absorption and act as signaling molecules that activate nuclear and membrane receptors. The vitamin D receptor (VDR) is a receptor for the active form of vitamin D and lithocholic acid (LCA), a secondary bile acid produced by the intestinal microflora. Unlike other bile acids that enter the enterohepatic circulation, LCA is poorly absorbed in the intestine. Although vitamin D signaling regulates various physiological functions, including calcium metabolism and inflammation/immunity, LCA signaling remains largely unknown. In this study, we investigated the effect of the oral administration of LCA on colitis in a mouse model using dextran sulfate sodium (DSS). Oral LCA decreased the disease activity of colitis in the early phase, which is a phenotype associated with the suppression of histological injury, such as inflammatory cell infiltration and goblet cell loss. These protective effects of LCA were abolished in VDR-deleted mice. LCA decreased the expression of inflammatory cytokine genes, but this effect was at least partly observed in VDR-deleted mice. The pharmacological effect of LCA on colitis was not associated with hypercalcemia, an adverse effect induced by vitamin D compounds. Therefore, LCA suppresses DSS-induced intestinal injury in its action as a VDR ligand.

Cellular metabolism: a link connecting cellular behaviour with the physiochemical properties of biomaterials for bone tissue engineering

Biomaterial properties, such as surface roughness, morphology, stiffness, conductivity, and chemistry, significantly influence a cell's ability to sense and adhere to its surface and regulate cell functioning. Understanding how biomaterial properties govern changes in cellular function is one of the fundamental goals of tissue engineering. Still, no generalized rule is established to predict cellular processes (adhesion, spreading, growth and differentiation) on biomaterial surfaces. A few studies have highlighted that cells sense biomaterial properties at multiple length scales and regulate various intracellular biochemical processes like cytoskeleton organization, gene regulation, and receptor expression to influence cell function. However, recent studies have found cellular metabolism as another critical aspect of cellular processes that regulate cell behavior, co-relating metabolism to cellular functions like adhesion, proliferation, and differentiation. Now researchers have started to uncover previously overlooked factors on how biomaterial properties govern changes in cellular functions mediated through metabolism. This review highlights how different physiochemical properties of scaffolds designed from different biomaterials influence cell metabolism. The review also discusses the role of metabolism change in cellular functions and cell behavior in the context of bone tissue engineering. It also emphasizes the importance of cell metabolism as a missing link between the cellular behavior and physicochemical properties of scaffolds and serves as a guiding principle for designing scaffolds for tissue engineering.

Vitamin D supplementation and exercise for improving physical function, body composition and metabolic health in overweight or obese older adults with vitamin D deficiency: a pilot randomized, double-blind, placebo-controlled trial

PURPOSE

Vitamin D supplementation may have non-skeletal health benefits and enhance exercise responsiveness, particularly in those with low vitamin D levels. We determined whether, compared with placebo, vitamin D supplementation taken prior to and during a 12-week exercise program improves physical function, body composition or metabolic health, in overweight and obese older adults with vitamin D deficiency.

METHODS

Fifty overweight or obese older adults (mean ± SD age: 60 ± 6 years; BMI 30.6 ± 5.7 kg/m²) with vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 50 nmol/L) were recruited. Participants were randomly allocated to receive either vitamin D₃ (4000 IU/day) or matching placebo for 24 weeks. Between weeks 12 and 24, all participants completed multi-modal exercise three days per week while continuing with vitamin D/placebo. Mean changes in physical function (primary outcome: gait speed), body composition and biochemical parameters at weeks 12 and 24 were compared between groups.

RESULTS

Vitamin D supplementation, with or without exercise, had no effect on gait speed. From baseline to week 12, vitamin D supplementation increased serum 25(OH)D levels (placebo: 2.5 ± 14.7 nmol/L; treatment: 43.4 ± 18.4 nmol/L; P < 0.001) and reduced stair climb times (placebo: 0.3 ± 1.0 s; treatment: - 0.2 ± 1.0 s; P = 0.046). From 12 to 24 weeks, vitamin D supplementation combined with exercise decreased waist circumference (placebo: 1.3 ± 7.3 cm; treatment: - 3.0 ± 6.1 cm; P = 0.02) and waist-to-hip ratio (placebo: 0.01 ± 0.05; treatment: - 0.03 ± 0.05; P = 0.01) relative to placebo. Vitamin D supplementation, with or without exercise, had no effect on other physical function, body composition or metabolic health outcomes.

CONCLUSION

Vitamin D supplementation had no effect on most physical function, body composition or metabolic health parameters when taken alone, or during exercise, in overweight or obese older adults with vitamin D deficiency. Vitamin D-related improvements in stair climb times and waist circumference suggest that future trials should explore the effects of vitamin D on muscle power, and its effects on body composition when combined with exercise, in populations with moderate or severe vitamin D deficiency.

Seven-month wintertime supplementation of 1200 IU vitamin D has no effect on hand grip strength in young, physically active males: A randomized, controlled study

Background

Study Design

Methods

Results

Conclusion

Muscle Function, Body Composition, Insulin Sensitivity and Physical Activity in Adolescents Born Preterm: Impact of Gestation and Vitamin D Status

Whilst several studies have explored adolescent metabolic and cognitive function after preterm birth, few have explored muscle function and physical activity. We set out to examine the relationship between gestational age and muscle metabolism in a cohort of adolescents who were born preterm. Participants were recruited from the Newcastle preterm birth growth study cohort. They did not have severe neurological disease and were not on daily medication. Participants underwent an assessment of oxidative muscle function using phosphorus magnetic resonance spectroscopy that included the half-time for recovery of equilibrium of phosphocreatine, τ½PCr. In addition, we measured key variables that might affect muscle function including physical activity levels determined by 3-day accelerometry, body composition using air displacement plethysmography, insulin sensitivity using the homeostatic model assessment/Matsuda index and serum vitamin D concentrations. 60 adolescents (35F) median age 15.6 years (range 12.1−18.8) with a median gestation of 31 weeks (range 24 to 34 weeks) underwent a single assessment. Males were more active and spent less time in sedentary mode. Time spent in light activity was associated with insulin sensitivity (IS) (Matsuda Index; p < 0.05) but there were no strong correlations between activity levels and gestational age. Greater fat mass, waist circumference and body mass index were all associated with lower IS. Gestational age was negatively associated with adjusted measures of oxidative muscle function (τ½PCr). In a stepwise multivariate linear regression model, gestational age at birth was the most significant predictor of oxidative muscle function (p = 0.005). Higher serum vitamin D levels were also associated with faster phosphocreatine recovery time (p = 0.045). Oxidative function in the skeletal muscle of adolescents born preterm is associated with gestational age and vitamin D concentrations. Our study suggests that being born preterm may have a long-term impact on muscle metabolism.

Vitamin D status modulates mitochondrial oxidative capacities in skeletal muscle: role in sarcopenia

Skeletal muscle mitochondrial function is the biggest component of whole-body energy output. Mitochondrial energy production during exercise is impaired in vitamin D-deficient subjects. In cultured myotubes, loss of vitamin D receptor (VDR) function decreases mitochondrial respiration rate and ATP production from oxidative phosphorylation. We aimed to examine the effects of vitamin D deficiency and supplementation on whole-body energy expenditure and muscle mitochondrial function in old rats, old mice, and human subjects. To gain further insight into the mechanisms involved, we used C2C12 and human muscle cells and transgenic mice with muscle-specific VDR tamoxifen-inducible deficiency. We observed that in vivo and in vitro vitamin D fluctuations changed mitochondrial biogenesis and oxidative activity in skeletal muscle. Vitamin D supplementation initiated in older people improved muscle mass and strength. We hypothesize that vitamin D supplementation is likely to help prevent not only sarcopenia but also sarcopenic obesity in vitamin D-deficient subjects.

Effects of Dietary Vitamin D Deficiency on Markers of Skeletal Muscle Mitochondrial Biogenesis and Dynamics

We examined the effects of dietary vitamin D deficiency on markers of mitochondrial biogenesis and dynamics in rat soleus muscle. Male Wistar rats were fed a chow with no vitamin D (No-D; 0 IU/kg) or a moderate dose (Mod-D; 2,000 IU/kg) of vitamin D chow for 8 wk. Compared to the Mod-D group, at 8 wk the No-D group showed significantly lower serum 25(OH)D levels. Although vitamin D deficiency had no effect on body composition, the No-D rats showed significantly decreased levels of PGC-1α, a marker of skeletal muscle mitochondrial biogenesis, and DRP1, a marker of skeletal muscle mitochondrial fission. The change in the PGC-1α protein expression and the serum 25(OH)D concentrations were significantly correlated. The change in DRP1 protein expression and the serum 25(OH)D concentrations tended to be correlated. There was no significant between-group difference in markers of mitochondrial fusion (MFN2 and OPA1) and mitophagy (PARKIN) in soleus muscle, and no relationship with serum 25(OH)D concentrations. Collectively our findings suggest that dietary vitamin D deficiency decreased PGC-1α and DRP1 protein expression in rat soleus muscle.

The Relationship Between Vitamin D and Activity of Daily Living in the Elderly

Objective

To analyze the association between vitamin D and the performance of activity of daily living in the elderly.

Methods

A total of 94 patients over the age of 65 were eligible to participate if they had undergone a bone mineral density test and if they were in a stable health condition. Subjects were further divided into two groups according to activity of daily living (ADL): the score over 40 of the patients as the high ADL group and the below as the low ADL group.

Results

According to univariate analysis, the mean of total hip T score, serum creatinine/cystatin C ratio (CCR), and vitamin D were significantly different between the two groups (P=0.024, 0.008, 0.010). Multivariate ORs showed that the CCR (OR: 0.948; 95%CI: 0.910–0.989; P=0.013) and vitamin D (OR: 865; 95%CI: 0.752–0.994; P=0.047) were inversely associated with having low ADL. Furthermore, on multiple linear regression analysis, the Barthel ADL index was related to geriatric nutritional risk index (GNRI), CCR and vitamin D but independent of patients’ age with the slope of 0.732, 0.539, and 0.689 separately, reflected the stronger relative within the variables.

Conclusion

We demonstrated that there is a negative correlation of CCR and vitamin D with having low ADL in elderly population. Monitoring the trend of serum vitamin D and CCR, may have a role in the early detection of low ADL with loss of muscle mass and strength in the population of the elderly.

Molecular Mechanisms Underlying Intensive Care Unit-Acquired Weakness and Sarcopenia

Skeletal muscle is a highly adaptable organ, and its amount declines under catabolic conditions such as critical illness. Aging is accompanied by a gradual loss of muscle, especially when physical activity decreases. Intensive care unit-acquired weakness is a common and highly serious neuromuscular complication in critically ill patients. It is a consequence of critical illness and is characterized by a systemic inflammatory response, leading to metabolic stress, that causes the development of multiple organ dysfunction. Muscle dysfunction is an important component of this syndrome, and the degree of catabolism corresponds to the severity of the condition. The population of critically ill is aging; thus, we face another negative effect-sarcopenia-the age-related decline of skeletal muscle mass and function. Low-grade inflammation gradually accumulates over time, inhibits proteosynthesis, worsens anabolic resistance, and increases insulin resistance. The cumulative consequence is a gradual decline in muscle recovery and muscle mass. The clinical manifestation for both of the above conditions is skeletal muscle weakness, with macromolecular damage, and a common mechanism-mitochondrial dysfunction. In this review, we compare the molecular mechanisms underlying the two types of muscle atrophy, and address questions regarding possible shared molecular mechanisms, and whether critical illness accelerates the aging process.

Roles of nutrition in muscle health of community-dwelling older adults: evidence-based expert consensus from Asian Working Group for Sarcopenia

General muscle health declines with age, and in particular, sarcopenia-defined as progressive loss of muscle mass and strength/physical performance-is a growing issue in Asia with a rising population of community-dwelling older adults. Several guidelines have addressed early identification of sarcopenia and management, and although nutrition is central to treatment of sarcopenia, there are currently few guidelines that have examined this specifically in the Asian population. Therefore, the Asian Working Group for Sarcopenia established a special interest group (SIG) comprising seven experts across Asia and one from Australia, to develop an evidence-based expert consensus. A systematic literature search was conducted using MEDLINE on the topic of muscle health, from 2016 (inclusive) to July 2021, in Asia or with relevance to healthy, Asian community-dwelling older adults (≥60 years old). Several key topics were identified: (1) nutritional status: malnutrition and screening; (2) diet and dietary factors; (3) nutritional supplementation; (4) lifestyle interventions plus nutrition; and (5) outcomes and assessment. Clinical questions were developed around these topics, leading to 14 consensus statements. Consensus was achieved using the modified Delphi method with two rounds of voting. Moreover, the consensus addressed the impacts of COVID-19 on nutrition, muscle health, and sarcopenia in Asia. These statements encompass clinical expertise and knowledge across Asia and are aligned with findings in the current literature, to provide a practical framework for addressing muscle health in the community, with the overall aim to encourage and facilitate broader access to equitable care for this target population.

Vitamin D Supplementation Improves Mitochondrial Function and Reduces Inflammation in Placentae of Obese Women

Background

About 30% of women entering pregnancy in the US are obese. We have previously reported mitochondrial dysregulation and increased inflammation in the placentae of obese women. Vitamin D (VitD) is a major player in calcium uptake and was shown to modulate mitochondrial respiration and the immune/inflammation system. Studies show decreased VitD levels in obese individuals; however, the effect of maternal obesity on VitD metabolism and its association with placental function remains understudied.

Methods

Maternal and cord blood plasma and placental samples were collected upon C-section from normal-weight (NW, body mass index [BMI]<25) and obese (OB, BMI>30) women with uncomplicated pregnancies at term. We measured 25(OH)D3 (calcidiol) levels in maternal and cord blood plasma using ELISA. We assessed the expression of CYP27B1, an activator of calcidiol, and Vitamin D receptor (VDR) in placentae from NW and OB, and women with gestational diabetes and preeclampsia. In addition, we examined the effects of VitD supplementation on mitochondrial function and inflammation in trophoblasts from NW and OB, using the Seahorse Bioanalyzer and Western blot, respectively.

Results

Vitamin D levels in blood from OB but not NW women and in cord blood from babies born to NW and OB women showed a significant inverse correlation with maternal pre-pregnancy BMI (r=-0.50, p<0.1 and r=-0.55, p=0.004 respectively). Cord plasma VitD levels showed a positive correlation with placental efficiency, i.e., the ratio between fetal and placental weight, as well as with maternal blood VitD levels (r=0.69 and 0.83 respectively, p<0.00). While we found no changes in CYP27B1 in OB vs. NW women, VDR expression were decreased by 50% (p<0.03) independent of fetal sex. No changes in VDR expression relative to BMI-matched controls were observed in the placentae of women with gestational diabetes or preeclampsia. Cytotrophoblasts isolated from placentae of OB women showed a dose-dependent increase in VDR expression after 24-hour treatment with calcitriol (10 nM and 100 nM), an active form of VitD. Trophoblasts isolated from OB women and treated with calcitriol improved mitochondrial respiration (p<0.05). We also found a two-fold increase in expression of the NLRP3 inflammasome and the pro-inflammatory cytokine IL-18 in trophoblasts isolated from placentae of OB women (p<0.05), with IL-18 expression being reversed by calcitriol treatment (100 nM).

Conclusions

We show that VitD deficiency is at least partially responsible for mitochondrial dysfunction and increased inflammation in the placentae of obese women. Vitamin D supplementation could be beneficial in improving placental dysfunction seen in obese women.

The Vitamin D/Vitamin D receptor (VDR) axis in muscle atrophy and sarcopenia

Muscle atrophy and sarcopenia (the term given to the age-related decline in muscle mass and function), influence an individuals risk of falls, frailty, functional decline, and, ultimately, impaired quality of life. Vitamin D deficiency (low serum levels of 25-hydroxyvitamin D (25(OH)D₃)) has been reported to impair muscle strength and increase risk of sarcopenia. The mechanisms that underpin the link between low 25(OH)D₃ and sarcopenia are yet to be fully understood but several lines of evidence have highlighted the importance of both genomic and non-genomic effects of active vitamin D (1,25-dihydroxyvitamin D (1,25(OH)₂D₃)) and its nuclear vitamin D receptor (VDR), in skeletal muscle functioning. Studies in vitro have demonstrated a key role for the vitamin D/VDR axis in regulating biological processes central to sarcopenic muscle atrophy, such as proteolysis, mitochondrial function, cellular senescence, and adiposity. The aim of this review is to provide a mechanistic overview of the proposed mechanisms for the vitamin D/VDR axis in sarcopenic muscle atrophy.

Vitamin D in Osteosarcopenic Obesity

Osteosarcopenic obesity is a unique clinical condition where low bone and muscle mass coexist in individuals with obesity. Alterations in adipose tissue, skeletal muscle and bone are strictly interconnected, and vitamin D plays key roles in several metabolic pathways that are involved in maintaining musculoskeletal health and glucose homeostasis. We reviewed the available literature on mechanisms underlying osteosarcopenic obesity, with a focus on the role of vitamin D in the pathogenesis and treatment of the condition. We found that, although evidence from large observational studies and pre-clinical experiments strongly supports a role of vitamin D deficiency in the pathogenesis of osteosarcopenic obesity, the common belief that vitamin D improves musculoskeletal health lacks solid clinical evidence, as trials specifically aimed at assessing the effects of vitamin D supplementation in patients with osteosarcopenic obesity are not available, and trials that investigated the role of vitamin D on muscle and bone health in other patient populations either showed no or even detrimental effects. We conclude that large observational and interventional studies including individuals with osteosarcopenic obesity representative of different sex, age and race are needed to better define the role of vitamin D in the pathogenesis and treatment of this condition.

Correlation between the Positive Effect of Vitamin D Supplementation and Physical Performance in Young Male Soccer Players

The aim of this study was to determine whether supplementation with vitamin D during eight weeks of high-intensity training influences muscle power and aerobic performance in young soccer players. A total of 25 athletes were divided into two groups: the supplemented group (GS; n = 12; vitamin D 20,000 IU, twice a week) and the non-supplemented group (GN; n = 13). A set of measurements, including sprint tests, explosive power test, maximal oxygen uptake (VO2max), and serum 25(OH)D concentration, were obtained before (T1) and after (T2) the intervention. A significant group x time interaction was found in the 25(OH)D serum levels (p = 0.002; ES = 0.36, large). A significant improvement in VO2max was found in the TG (p = 0.0004) and the GS (p = 0.031). Moreover, a positive correlation between 25(OH)D and VO2max (R = 0.4192, p = 0.0024) was calculated. The explosive power tests revealed insignificant time interactions in the average 10-jump height and average 10-jump power (p = 0.07, ES = 0.13; p = 0.10, ES = 0.11, respectively). A statistically insignificant trend was observed only in the group-by-time interaction for the sprint of 10 m (p = 0.05; ES = 0.15, large). The present study provides evidence that vitamin D supplementation has a positive but trivial impact on the explosive power and locomotor skills of young soccer players, but could significantly affect their aerobic performance.

Vitamin D Impacts on Skeletal Muscle Dysfunction in Patients with COPD Promoting Mitochondrial Health

Skeletal muscle dysfunction is frequently associated with chronic obstructive pulmonary disease (COPD), which is characterized by a permanent airflow limitation, with a worsening respiratory disorder during disease evolution. In COPD, the pathophysiological changes related to the chronic inflammatory state affect oxidant–antioxidant balance, which is one of the main mechanisms accompanying extra-pulmonary comorbidity such as muscle wasting. Muscle impairment is characterized by alterations on muscle fiber architecture, contractile protein integrity, and mitochondrial dysfunction. Exogenous and endogenous sources of reactive oxygen species (ROS) are present in COPD pathology. One of the endogenous sources of ROS is represented by mitochondria. Evidence demonstrated that vitamin D plays a crucial role for the maintenance of skeletal muscle health. Vitamin D deficiency affects oxidative stress and mitochondrial function influencing disease course through an effect on muscle function in COPD patients. This review will focus on vitamin-D-linked mechanisms that could modulate and ameliorate the damage response to free radicals in muscle fibers, evaluating vitamin D supplementation with enough potent effect to contrast mitochondrial impairment, but which avoids potential severe side effects.

Vitamin D and Ocular Diseases: A Systematic Review

The contributory roles of vitamin D in ocular and visual health have long been discussed, with numerous studies pointing to the adverse effects of vitamin D deficiency. In this paper, we provide a systematic review of recent findings on the association between vitamin D and different ocular diseases, including myopia, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), dry eye syndrome (DES), thyroid eye disease (TED), uveitis, retinoblastoma (RB), cataract, and others, from epidemiological, clinical and basic studies, and briefly discuss vitamin D metabolism in the eye. We searched two research databases for articles examining the association between vitamin D deficiency and different ocular diseases. One hundred and sixty-two studies were found. There is evidence on the association between vitamin D and myopia, AMD, DR, and DES. Overall, 17 out of 27 studies reported an association between vitamin D and AMD, while 48 out of 54 studies reported that vitamin D was associated with DR, and 25 out of 27 studies reported an association between vitamin D and DES. However, the available evidence for the association with other ocular diseases, such as glaucoma, TED, and RB, remains limited.

Hypothesized pathways for the association of vitamin D status and insulin sensitivity with resting energy expenditure: a cross sectional mediation analysis in Australian adults of European ancestry

Background

The role of vitamin D in human energy expenditure requires confirmation. We explored whether insulin sensitivity (IS)/insulin resistance (IR) mediated the association of vitamin D status (25OHD) on resting energy expenditure (REE).

Methods

REE, body composition (by DEXA) and clinical biochemistry of 155 Australian men and women were collated. A hypothesized mediation pathway through IS/IR on the direct association between 25OHD and REE was modeled, using three surrogate indices of IS/IR: McAuley’s insulin sensitivity index (McA), Quantitative insulin sensitivity check index (QUICKI) and triglyceride to glucose ratio (TYG). The modeling was performed on PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with and without the adjustment for covariates.

Results

Unadjusted models indicated a sizeable negative mediation by all IS/IR indices but no significant direct effect of 25OHD on REE. On adjustment for covariates, a negative indirect mediation effect of McA [β coefficient (SE) −2.1(0.821); bootstrapped 95% CI:−3.934, −0.703; p < 0.05] and a similar negative mediation of TYG [−1.935 (0.780); bootstrapped 95% CI: (−3.679, −0.622; p < 0.05] was observed. These models also showed a positive direct effect of 25OHD on REE. In contrast, QUICKI made a smaller contribution to the total effect though in the same direction as the other two measures [−0.783 (0.534); bootstrapped 95% CI: (−1.939, 0.134; P > 0.05].

Conclusions

A sizeable, partial, negative mediation of IS/IR on the direct relationship between 25OHD and REE, dampened the total effect of vitamin D on REE. Validation of the proposed causal framework would clarify vitamin D’s role in human energy metabolism.

Resting Metabolic Rate in Women with Endocrine and Osteoporotic Disorders in Relation to Nutritional Status, Diet and 25(OH)D Concentration

There are speculations that vitamin D may be an important regulator of the energy metabolism. The aim of this study was to evaluate the influence of serum 25(OH)D concentration and nutritional status on the resting metabolic rate. The study group consisted of 223 women with endocrine and/or osteoporotic disorders. The control group consisted of 108 women, clinically healthy. The total 25(OH)D concentration level was measured with an assay using chemiluminescent immunoassay technology. Indirect calorimetry was applied to assess the resting metabolic rate. The mean resting metabolic rate was significantly lower in the group of women with metabolic disorders than in the control group. A correlation was found between serum 25(OH)D levels in healthy subjects and the resting metabolic rate. Significantly higher resting metabolic rate was found in women with normal serum 25(OH)D levels in comparison to subjects with deficient vitamin D levels. The control group demonstrated a relationship between body fat tissue and fat-free body mass and the resting metabolic rate. Both 25(OH)D concentration and body composition were factors influencing the resting metabolic rate in the group of healthy subjects. More research is needed to clarify the relationship between vitamin D status and metabolic rate in individuals with endocrine and osteoporotic disorders.

Sex-Specific Catabolic Metabolism Alterations in the Critically Ill following High Dose Vitamin D

Pharmacological interventions are essential for the treatment and management of critical illness. Although women comprise a large proportion of the critically ill, sex-specific pharmacological properties are poorly described in critical care. The sex-specific effects of vitamin D₃ treatment in the critically ill are not known. Therefore, we performed a metabolomics cohort study with 1215 plasma samples from 428 patients from the VITdAL-ICU trial to study sex-specific differences in the metabolic response to critical illness following high-dose oral vitamin D₃ intervention. In women, despite the dose of vitamin D₃ being higher, pharmacokinetics demonstrated a lower extent of vitamin D₃ absorption compared to men. Metabolic response to high-dose oral vitamin D₃ is sex-specific. Sex-stratified individual metabolite associations with elevations in 25(OH)D following intervention showed female-specific positive associations in long-chain acylcarnitines and male-specific positive associations in free fatty acids. In subjects who responded to vitamin D₃ intervention, significant negative associations were observed in short-chain acylcarnitines and branched chain amino acid metabolites in women as compared to men. Acylcarnitines and branched chain amino acids are reflective of fatty acid B oxidation, and bioenergesis may represent notable metabolic signatures of the sex-specific response to vitamin D. Demonstrating sex-specific pharmacometabolomics differences following intervention is an important movement towards the understanding of personalized medicine.

From the Bench to the Bedside: Branched Amino Acid and Micronutrient Strategies to Improve Mitochondrial Dysfunction Leading to Sarcopenia

With extended life expectancy, the older population is constantly increasing, and consequently, so too is the prevalence of age-related disorders. Sarcopenia, the pathological age-related loss of muscle mass and function; and malnutrition, the imbalance in nutrient intake and resultant energy production, are both commonly occurring conditions in old adults. Altered nutrition plays a crucial role in the onset of sarcopenia, and both these disorders are associated with detrimental consequences for patients (e.g., frailty, morbidity, and mortality) and society (e.g., healthcare costs). Importantly, sarcopenia and malnutrition also share critical molecular alterations, such as mitochondrial dysfunction, increased oxidative stress, and a chronic state of low grade and sterile inflammation, defined as inflammageing. Given the connection between malnutrition and sarcopenia, nutritional interventions capable of affecting mitochondrial health and correcting inflammageing are emerging as possible strategies to target sarcopenia. Here, we discuss mitochondrial dysfunction, oxidative stress, and inflammageing as key features leading to sarcopenia. Moreover, we examine the effects of some branched amino acids, omega-3 PUFA, and selected micronutrients on these pathways, and their potential role in modulating sarcopenia, warranting further clinical investigation.

Reactive Oxygen Species (ROS) and Antioxidants as Immunomodulators in Exercise: Implications for Heme Oxygenase and Bilirubin

Exercise is commonly prescribed as a lifestyle treatment for chronic metabolic diseases as it functions as an insulin sensitizer, cardio-protectant, and essential lifestyle tool for effective weight maintenance. Exercise boosts the production of reactive oxygen species (ROS) and subsequent transient oxidative damage, which also upregulates counterbalancing endogenous antioxidants to protect from ROS-induced damage and inflammation. Exercise elevates heme oxygenase-1 (HO-1) and biliverdin reductase A (BVRA) expression as built-in protective mechanisms, which produce the most potent antioxidant, bilirubin. Together, these mitigate inflammation and adiposity. Moderately raising plasma bilirubin protects in two ways: (1) via its antioxidant capacity to reduce ROS and inflammation, and (2) its newly defined function as a hormone that activates the nuclear receptor transcription factor PPARα. It is now understood that increasing plasma bilirubin can also drive metabolic adaptions, which improve deleterious outcomes of weight gain and obesity, such as inflammation, type II diabetes, and cardiovascular diseases. The main objective of this review is to describe the function of bilirubin as an antioxidant and metabolic hormone and how the HO-1-BVRA-bilirubin-PPARα axis influences inflammation, metabolic function and interacts with exercise to improve outcomes of weight management.

An Expert Perspective on Phosphate Dysregulation With a Focus on Chronic Hypophosphatemia

Because of their rarity, diseases characterized by chronic hypophosphatemia can be underrecognized and suboptimally managed, resulting in poor clinical outcomes. Moreover, serum phosphate may not be measured routinely in primary care practice. Authors participated in several working sessions to advance the understanding of phosphate homeostasis and the causes, consequences, and clinical implications of chronic hypophosphatemia. Phosphate levels are regulated from birth to adulthood. Dysregulation of phosphate homeostasis can result in hypophosphatemia, which becomes chronic if phosphate levels cannot be normalized. Chronic hypophosphatemia may be underrecognized as serum phosphate measurement is not always part of routine analysis in the primary care setting and results might be misinterpreted, for instance, due to age-specific differences not being accounted for and circadian variations. Clinical consequences of chronic hypophosphatemia involve disordered endocrine regulation, affect multiple organ systems, and vary depending on patient age and the underlying disorder. Signs and symptoms of chronic hypophosphatemic diseases that manifest during childhood or adolescence persist into adulthood if the disease is inadequately managed, resulting in an accumulation of clinical deficits and a progressive, debilitating impact on quality of life. Early identification and diagnosis of patients with chronic hypophosphatemia is crucial, and clinical management should be started as soon as possible to maximize the likelihood of improving health outcomes. Furthermore, in the absence of a universally accepted description for "chronic hypophosphatemia," a definition is proposed here that aims to raise awareness of these diseases, facilitate diagnosis, and guide optimal phosphate management strategies by improving monitoring and assessment of patient response to treatment. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

High Serum AST/ALT Ratio and Low Serum INS*PA Product Are Risk Factors and Can Diagnose Sarcopenia in Middle-Aged and Older Adults

BACKGROUND

Sarcopenia is an age-related clinical condition and associated with an increased risk of adverse outcomes. However, to date, there is no global standard for the diagnosis of sarcopenia, and fewer serum biomarkers have been suggested for the diagnosis of sarcopenia. It is, thus, important that sarcopenia-related serological diagnostic markers be explored. The present study was based on the Asian Working Group on Sarcopenia 2019 (AWGS 2019) criteria to assess whether aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio and fasting insulin*prealbumin (INS*PA) product are diagnostic markers associated with sarcopenia in various ethnic groups in western China.

METHODS

This cross-sectional study included 4,099 adults (1,471 men and 2,628 women) from the West China Health and Aging Trend (WCHAT) study. The value of serum biomarkers was based on laboratory data. The accompanying metabolic disorders and the associated parameters were evaluated. Logistic regression analysis was used to explore the association between markers and sarcopenia. Receiver operating characteristic curve (ROC) analysis was used to evaluate the diagnostic efficacy of the test in differentiating sarcopenia.

RESULTS

Binary regression analysis showed that high serum AST/ALT (OR = 2.247) and adrenal cortisol (PTC, OR = 1.511), low serum INS*PA (OR = 2.970), free triiodothyronine (FT3, OR = 1.313), 25-OH-VitD (VitD, in male participants, OR = 1.817), and diastolic blood pressure (DBP, in female subjects, OR = 1.250) were independent risk factors for sarcopenia (P < 0.05). AST/ALT and INS*PA were not affected by metabolic factors and had better diagnostic efficacy for sarcopenia. The AUC of the INS*PA was the highest (0.705, 0.706, and 0.701, respectively, P < 0.05), followed by that of the AST/ALT (0.680, 0.675, and 0.695, respectively, P < 0.05). The AUC of the AST/ALT/(INS*PA)*10,000 used to diagnose sarcopenia was 0.727.

CONCLUSION

Among middle-aged and older adults of multiple ethnicities in western China, we found that higher AST/ALT and lower INS*PA levels are associated with an increased prevalence of sarcopenia. Since these serum biomarkers are inexpensive and can be obtained easily from biochemical routine, regular follow-up of AST/ALT and INS*PA may be an effective strategy in sarcopenia screening and management.

The Atrophic Effect of 1,25(OH)2 Vitamin D3 (Calcitriol) on C2C12 Myotubes Depends on Oxidative Stress

Dysfunctional mitochondrial metabolism has been linked to skeletal muscle loss in several physio-pathological states. Although it has been reported that vitamin D (VD) supports cellular redox homeostasis by maintaining normal mitochondrial functions, and VD deficiency often occurs in conditions associated with skeletal muscle loss, the efficacy of VD supplementation to overcome muscle wasting is debated. Investigations on the direct effects of VD metabolites on skeletal muscle using C2C12 myotubes have revealed an unexpected pro-atrophic activity of calcitriol (1,25VD), while its upstream metabolites cholecalciferol (VD3) and calcidiol (25VD) have anti-atrophic effects. Here, we investigated if the atrophic effects of 1,25VD on myotubes depend on its activity on mitochondrial metabolism. The impact of 1,25VD and its upstream metabolites VD3 and 25VD on mitochondria dynamics and the activity of C2C12 myotubes was evaluated by measuring mitochondrial content, architecture, metabolism, and reactive oxygen species (ROS) production. We found that 1,25VD induces atrophy through protein kinase C (PKC)-mediated ROS production, mainly of extramitochondrial origin. Consistent with this, cotreatment with the antioxidant N-acetylcysteine (NAC), but not with the mitochondria-specific antioxidant mitoTEMPO, was sufficient to blunt the atrophic activity of 1,25VD. In contrast, VD3 and 25VD have antioxidant properties, suggesting that the efficacy of VD supplementation might result from the balance between atrophic pro-oxidant (1,25VD) and protective antioxidant (VD3 and 25VD) metabolites.

Role of vitamin D in diabetic retinopathy: Pathophysiological and clinical aspects

Epidemiological data predict a dramatic increase in the prevalence of diabetes and of diabetic retinopathy (DR) - the most common complication of diabetes-for which however we do not have so far effective tools for prevention and treatment. Since hypovitaminosis D is very frequent in patients with diabetes and vitamin D (VD) has vascular protective properties, several studies have addressed the association of VD deficiency with DR and its severity and progression, whereas the effects of VD supplementation on its natural history are largely unknown. Here we review the available evidence that supports the possible protective role of VD in DR and suggests to determine the VD levels in DR patients calling for a definitive randomized clinical trial to ascertain whether VD supplementation could protect against DR.

Effect of Vitamin D Supplementation on the Prognosis of Post-stroke Fatigue: A Retrospective Cohort Study

Objective: We aimed to evaluate the effect of vitamin D supplementation in post-stroke fatigue (PSF) patients with vitamin D deficiency on fatigue symptoms and outcomes. Methods: Patients with primary acute ischemic stroke (AIS) were recruited consecutively from July 2016 to June 2018. Post-stroke fatigue patients were screened out with the Fatigue Severity Scale (FSS) questionnaire, serum concentrations of 25-hydroxyvitamin D [25-(OH)-D] were assessed with enzyme-linked immunosorbent assay (ELISA), and neurological function was evaluated with FSS and modified Rankin Scale (mRS) scoring criteria. Post-stroke fatigue patients with vitamin D deficiency were divided into two groups: a study group in which patients received vitamin D supplementation (cholecalciferol, 600 IU/day) along with usual care, and a control group in which patients received usual care alone. At the end of 1 and 3 months after treatment, all PSE patients accepted re-measurement of serum vitamin D and re-evaluation of fatigue and neurological function. Results: A total of 532 AIS patients were consecutively recruited to participate in this study. Patients without PSF, non-vitamin D deficiency, pre-stroke fatigue, or vitamin D supplementation were excluded from the study. In addition, patients who were lost to follow-up were also excluded. Finally, 139 out of 532 (26.1%) patients with PSF and vitamin D deficiency received vitamin D supplementation treatment. Fatigue Severity Scale score was significantly lower in the study group than in the control group at 1 month (t = -4.731, p < 0.01) and 3 months (t = -7.937, p < 0.01) after treatment. One month after treatment, mRS score in the study group was lower than that in the control group without statistical difference (t = -0.660, p > 0.05), whereas mRS was significantly higher in the study group than in the control group at 3 months after treatment (t = -4.715, p < 0.01). Conclusions: Our results indicated that vitamin D supplementation could improve fatigue symptoms and neurological outcomes in PSF patients with vitamin D deficiency. Subject to replication in other settings, a randomized controlled trial (RCT) might be undertaken to validate the potential beneficial impact of vitamin D supplementation in post-stroke patients found to be vitamin D deficient.

The Impact of Vegan and Vegetarian Diets on Physical Performance and Molecular Signaling in Skeletal Muscle

Muscular adaptations can be triggered by exercise and diet. As vegan and vegetarian diets differ in nutrient composition compared to an omnivorous diet, a change in dietary regimen might alter physiological responses to physical exercise and influence physical performance. Mitochondria abundance, muscle capillary density, hemoglobin concentration, endothelial function, functional heart morphology and availability of carbohydrates affect endurance performance and can be influenced by diet. Based on these factors, a vegan and vegetarian diet possesses potentially advantageous properties for endurance performance. Properties of the contractile elements, muscle protein synthesis, the neuromuscular system and phosphagen availability affect strength performance and can also be influenced by diet. However, a vegan and vegetarian diet possesses potentially disadvantageous properties for strength performance. Current research has failed to demonstrate consistent differences of performance between diets but a trend towards improved performance after vegetarian and vegan diets for both endurance and strength exercise has been shown. Importantly, diet alters molecular signaling via leucine, creatine, DHA and EPA that directly modulates skeletal muscle adaptation. By changing the gut microbiome, diet can modulate signaling through the production of SFCA.

Serum vitamin D status inversely associates with a prevalence of severe sarcopenia among female patients with rheumatoid arthritis

Sarcopenia is an age-related disease with an increased risk of mortality. It is emerging that low serum 25-hydroxyvitamin D [25(OH)D] affects the sarcopenic state in general, but in rheumatoid arthritis (RA), these associations are not understood although the prevalence of vitamin D insufficiency is high in RA. We conducted a cross-sectional study of older female outpatients from our cohort (KURAMA) database. We measured skeletal muscle mass, handgrip strength, and gait-speed to diagnose severe sarcopenia. The serum 25(OH)D concentration was measured using electrochemiluminescence immunoassay. A total of 156 female patients with RA (sarcopenia:44.9%, severe sarcopenia: 29.5%, and without sarcopenia: 25.6%) were enrolled. Classification of vitamin D status at a cutoff point of median 25(OH)D concentration revealed that low 25(OH)D status was associated with a high prevalence of severe sarcopenia and with low measured values of muscle mass, handgrip, and gait speed. Furthermore, multivariable logistic regression analysis identified that low 25(OH)D status was associated with a high prevalence of severe sarcopenia (OR 6.00; 95% CI 1.99-18.08).The same association was observed when the cut-off value was set at 20 ng/ml. In components of sarcopenia, both low physical performance and muscle mass were associated with low 25(OH)D status. In conclusion, vitamin D status was inversely associated with severe sarcopenia, low physical performance, and low skeletal muscle mass. Modification of vitamin D status including vitamin D supplementation should be investigated as a therapeutic strategy for sarcopenic patients with RA.

Muscle Regeneration and Function in Sports: A Focus on Vitamin D

Muscle is one of the main targets for the biological effects of vitamin D. This hormone modulates several functions of skeletal muscles, from development to tissue repair after injury, through genomic and non-genomic mechanisms. Vitamin D deficiency and supplementation seem to significantly affect muscle strength in different populations, including athletes, although optimal serum 25(OH)D3 level for sport performance has not been defined so far. Additionally, vitamin D deficiency results in myopathy characterized by fast-twitch fiber atrophy, fatty infiltration, and fibrosis. However, less is known about regenerative effects of vitamin D supplementation after sport-related muscle injuries. Vitamin D receptor (VDR) is particularly expressed in the embryonic mesoderm during intrauterine life and in satellite cells at all stages of life for recovery of the skeletal muscle after injury. Vitamin D supplementation enhances muscle differentiation, growth, and regeneration by increasing the expression of myogenic factors in satellite cells. The objective of this narrative review is to describe the role of vitamin D in sport-related muscle injury and tissue regeneration.