Multi-vitamin supplementation blunts the circulating IL-6/IL-10 ratio increase after knee arthroplasty: A randomized, double-blind, placebo controlled study.

Circulating interleukin (IL)-6 and IL-10 concentrations can be elevated following the surgically induced trauma of total knee arthroplasty (TKA). An exaggerated increase in IL-6 relative to IL-10 (i.e., IL-6/IL-10 ratio) associates with trauma severity and indicative of pro-inflammatory predominance. Although various vitamins and minerals alter individual IL-6 and IL-10 concentrations in the blood, surprisingly, it is unknown if a multi-vitamin supplement alters the IL-6/IL-10 ratio during the systemic inflammatory response following TKA. The objective of this study was to identify if a multi-vitamin with mineral supplement taken prior to alters the circulating IL-6/IL-10 ratio following total knee arthroplasty (TKA). This study consisted of a randomized, double-blind, placebo controlled design. Twenty-one subjects undergoing elective, primary, unilateral TKA were randomly assigned to a placebo (PL, n = 11) or multi-vitamin with mineral supplement (MV, n = 10). Supplements were taken daily starting approximately 6-weeks prior to surgery. Supplements were not taken the day of surgery or during inpatient care 2-days after surgery. Circulating IL-6, IL-10, high-sensitivity CRP (hsCRP), vitamin C (ascorbic acid (AA)), vitamin D (25-hydroxyvitamin D (25(OH)D)), and vitamin E (α-tocopherol (αT)) concentrations were measured in fasting blood draw samples obtained ~6-weeks prior to surgery (and before starting supplementation), the morning of surgery, and 24-hours and 48-hours after surgery. MV supplementation tended to increase serum 25(OH)D and significantly increased plasma AA and plasma αT before surgery without mitigating the post-operative IL-6 and hsCRP increases. However, the post-operative increase in the serum IL-6/IL-10 ratio after surgery was significantly blunted in the MV group. Based on these findings, we conclude that a multi-vitamin with mineral supplement taken daily for several weeks before surgery might reduce the pro-inflammatory predominance after TKA. Future research confirming or refuting the novel data presented herein is needed.

Circulating IL-10 is compromised in patients predisposed to developing and in patients with severe knee osteoarthritis.

The purpose of this investigation was to identify if serum interleukin (IL)-10 and tumor necrosis factor (TNF)-α concentrations and their ratio (IL-10/TNF-α) are altered in subjects predisposed to developing knee osteoarthritis following ligamentous injury and in those with severe knee osteoarthritis. Serum IL-10 and TNF-α concentrations were measured in four groups of subjects (n = 218): (1) reportedly-healthy and non-injured control subjects (CON; n = 92), (2) subjects scheduled to undergo anterior cruciate ligament surgery (ACL; n = 42), (3) non-surgical subjects with knee osteoarthritis (OA; n = 60), and (4) subjects with knee osteoarthritis scheduled to undergo total knee arthroplasty (TKA; n = 24). X-ray images were used to grade the severity of knee osteoarthritis. Serum IL-10 and the serum IL-10/TNF-α ratio were significantly lower while serum TNF-α was not significantly perturbed with severe compared to moderate knee osteoarthritis (i.e., Kellgren-Lawrence grade 4 vs. 3, respectively). Serum IL-10 was significantly lower in the absence of serum TNF-α alterations in the ACL group. We conclude that serum IL-10 concentrations are compromised in subjects predisposed to developing knee osteoarthritis following ligamentous trauma and in subjects with radiographic evidence of severe knee osteoarthritis.

Muscular-based and patient-reported outcomes differentially associate with circulating superoxide dismutases and cytokines in knee osteoarthritis.

Muscular (i.e., quadriceps) weakness contributes to disease progression and precedes the appearance of patient-reported symptoms, such as pain and perceived physical dysfunction, in knee osteoarthritis (OA). It is unknown, however, if muscular-based and patient-reported outcomes differentially associate with systemic biomarkers reflective of the local mediators in knee OA. The purpose of this study was to identify if muscular-based and patient-reported outcomes differentially associate with circulating superoxide dismutase (SOD) and cytokines in knee OA. Subjects (n = 29) with pain, muscular weakness, and radiographic evidence (Kellgren-Lawrence grade ≥2) of knee OA in the involved (INV) leg were included in this study. Serum Cu/Zn and Mn SOD and cytokine concentrations were measured in fasting blood samples. Pain and physical dysfunction were subjectively assessed and muscle strength (i.e., peak isometric force and torque, and peak isokinetic-concentric knee-extension and -flexion torques) was determined unilaterally in the INV and non-involved (NI) legs. Peak isometric and peak isokinetic-concentric knee-flexion torques in the INV leg correlated with serum Cu/Zn SOD (both p < 0.05). Peak isometric force and torque and peak isokinetic-concentric knee-extension and -flexion torques in the INV leg correlated with serum Mn SOD (all p < 0.05). Pain and dysfunction inversely associated with serum IL-1ß, IL-4, IL-5, IL-12, IL-13, and/or IFN-γ (p < 0.05). Neither SOD associated with pain or dysfunction, and none of the cytokines associated with muscular-based outcomes. We conclude that common outcome measures used in the clinical evaluation of OA differentially associate with circulating SOD and cytokines.

Tourniquet use during total knee arthroplasty does not modulate the neutrophil-to-lymphocyte ratio, pain, or activity.

The purpose of our study was to identify the influence of tourniquet use during total knee arthroplasty (TKA) on the neutrophil-to-lymphocyte ratio (NLR) shortly after surgery and patient-reported outcomes (pain and physical activity) from outpatient physical therapy. This retrospective study consisted of 104 subjects who underwent primary unilateral TKA (51 subjects with and 53 subjects without tourniquet assistance) between 2010 and 2012. The NLR was calculated from the absolute neutrophil and lymphocyte counts obtained immediately before and after (1 and 2 days) knee arthroplasty. The Knee Outcome Survey (KOS) of Activities of Daily Living and numeric pain scores collected at the first [33.0 (34.2) days after surgery] and last [85.5 (40.7) days after surgery] outpatient physical therapy visits were extracted from an electronic database. The NLR, pain, and KOS score were not significantly (all p > 0.05) different with tourniquet use. Based on these findings, we conclude that tourniquet use during TKA neither increases systemic inflammation shortly after surgery nor impairs patient-reported outcomes obtained during outpatient physical therapy. LEVEL OF EVIDENCE: IV.

Circulating interleukin-6 is not altered while γ-tocopherol is increased in subjects scheduled for knee surgery with low vitamin D.

The purpose of this study was to identify if circulating interleukin (IL)-6 and γ-tocopherol (γT) fluctuate with vitamin D status in subjects with an underlying knee joint injury or disease. We hypothesized that low vitamin D associates with an increase in plasma γT while serum IL-6 remains unchanged in subjects with an underlying knee joint trauma or disease. Fifty-four subjects scheduled to undergo primary, unilateral anterior cruciate ligament reconstructive surgery (ACL; n=27) or total knee arthroplasty (TKA; n=27) were studied. Circulating γT, α-tocopherol (αT), lipids (cholesterol and triglycerides), IL-6, and 25-hydroxyvitamin D (25(OH)D) were measured in fasting blood samples obtained prior to surgery. Subjects were classified as vitamin D deficient, insufficient, or sufficient if they had a serum 25(OH)D concentration <50, 50-75, or >75nM, respectively. The majority (57%) of the subjects possessed a serum 25(OH)D less than 50nM. Circulating cholesterol, triglycerides, and IL-6 were not significantly (all p>0.05) different between vitamin D status groups. However, lipid corrected αT was significantly (p<0.05) decreased and both lipid- and non-lipid-corrected plasma γT concentrations were significantly (both p<0.05) increased with low serum 25(OH)D (i.e., <50nM). A significant (p<0.05) multi-variate analysis revealed that an increase in plasma γT per lipids was significantly (p<0.05) predicted by a decrease in serum 25(OH)D but not by a decrease in plasma αT per lipids. We conclude that low vitamin D associates with an increase in plasma γT but not IL-6 in subjects with an underlying joint injury or disease.

Is there a link between the neutrophil-to-lymphocyte ratio and venous thromboembolic events after knee arthroplasty? A pilot study.

BACKGROUND: This study aimed to identify (1) if the postoperative increase in the neutrophil-to-lymphocyte ratio (NLR) is different between contrasting knee arthroplasty procedures, and (2) if the NLR predicts venous thromboembolism (VTE) after total knee arthroplasty (TKA). MATERIALS AND METHODS: To address the first objective, we retrospectively studied patients who underwent primary unilateral TKA (n = 111) or unicompartmental knee arthroplasty (UKA; n = 74) between 2009 and 2012. Patients who required a blood transfusion, underwent autologous blood salvage, experienced any postoperative complication (such as VTE), or were re-admitted >90 days were excluded from analysis. For the second objective, we retrospectively identified patients (cases, n = 10) who underwent primary unilateral TKA between 2010 and 2012 and developed postoperative VTE (deep venous thrombosis, pulmonary embolism, or both) during inpatient care (postoperative day 1 or day 2). Cases were matched to surgeon, gender, body mass index, age, and date of surgery controls (n = 20) who underwent primary unilateral TKA without developing VTE before patient discharge. The NLR was calculated from the neutrophil and lymphocyte counts extracted from pre- and postoperative (day 1 and day 2) blood chemistry records. RESULTS: On postoperative day 1, the NLR increase was exacerbated (p = 0.02) following TKA compared to UKA and predicted (p = 0.02) the occurrence of VTE in TKA patients prior to hospital discharge. CONCLUSION: We conclude that the NLR increase is greater following TKA compared to UKA and could serve as a matrix to predict or identify a patient susceptible of sustaining VTE after TKA. LEVEL OF EVIDENCE: 3.

Serum cytokines and muscle strength after anterior cruciate ligament surgery are not modulated by high-doses of vitamins E (α- and γ-tocopherol's) and C.

The purpose of this investigation was to identify if supplemental vitamin E (consisting of α- and γ-tocopherol's) and C modulate serum cytokine and muscle strength following an ACL injury and surgery. Subjects were randomly assigned to one of two groups: (1) placebo (n=14) or (2) vitamins E (α-[600m g RRR-α-tocopherol, αT] and γ-[600 mg of RRR-γT]) and C (1000 mg ascorbic acid, AA) (EC; n=15). Supplements were taken daily starting ∼2-wk prior to and concluding 16-wk after surgery. Fasting blood samples were obtained and single-leg peak isometric force measurements were performed at baseline (prior to supplementation), before surgery (∼120-min - blood draw only), and 8-wk, 12-wk, and 16-wk after surgery. αT, γT, AA, and cytokines were measured in each blood sample, and peak isometric force was measured on the injured and non-injured legs separately at each testing session. An exercise protocol consisting of repetitive knee and hip extension and flexion contractions to exhaustion was performed on the injured limb at 16-wk. Vitamin E and C supplementation significantly (all p<0.05) increased plasma αT (∼40%), γT (∼160%), and AA (∼50%) concentrations. Serum cytokine concentrations, peak isometric force, and time to exhaustion during the exercise protocol were not significantly different between groups. Based on these findings, we conclude that vitamin E and C supplementation increases their endogenous levels without minimizing muscular weakness or modulating serum cytokine concentrations after ACL surgery.

Improvement in muscle strength after an anterior cruciate ligament injury corresponds with a decrease in serum cytokines.

The purpose of this communication was to identify if a decrease in serum cytokine concentrations associates with an improvement in muscle strength after an anterior cruciate ligament (ACL) injury. To establish groups with contrasting serum cytokine concentrations, subjects scheduled for ACL reconstructive surgery were separated into one of two groups (gender matched) based on their time from injury occurrence: (1) Early (<21-d from injury occurrence; n=22) or (2) Late (⩾21-d from injury occurrence; n=22). Before surgery, each subject provided a fasting blood sample and performed single-leg peak isometric force testing on the injured (INJ) and non-injured (NI) limbs. Compared to the NI limb, peak isometric force in the INJ limb was decreased (p<0.05) in both groups (Early, ∼35%; Late, ∼18%). The deficit in peak isometric force, however, was increased (p<0.05) in the Early compared to Late group. Similarly, serum granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-6, and IL-13 were increased (all p<0.05) in the Early group. These unique findings show a concurrent increase in muscular weakness and serum cytokine concentrations shortly after (<21-d) an ACL injury. Importantly, muscular weakness persisted thereafter (⩾21-d) but at an attenuated level and parallel to a decrease in circulating cytokine concentrations. We conclude that a decrease in serum cytokines associates with a reduction in muscular weakness after an ACL injury.

Supplemental vitamin D increases serum cytokines in those with initially low 25-hydroxyvitamin D: a randomized, double blind, placebo-controlled study.

The purpose of this study was to determine if vitamin D status before supplementation influences the cytokine response after supplemental vitamin D. Forty-six reportedly healthy adults (mean(SD); age, 32(7) y; body mass index (BMI), 25.3(4.5) kg/m(2); serum 25-hydroxyvitamin D (25(OH)D), 34.8(12.2) ng/mL) were randomly assigned (double blind) to one of three groups: (1) placebo (n=15), or supplemental vitamin D (cholecalciferol) at (2) 4000 (n=14) or (3) 8000IU (n=17). Supplements were taken daily for 35days. Fasting blood samples were obtained before (Baseline, Bsl) and 35-days after (35-d) supplementation. Serum 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)D), cytokines, and intact parathyroid hormone with calcium were measured in each blood sample. Supplemental vitamin D increased serum 25(OH)D (4000IU, ≈29%; 8000IU, ≈57%) and 1,25(OH)D (4000IU, ≈12%; 8000IU, ≈38%) without altering intact parathyroid hormone or calcium. The vitamin D metabolite increases in the supplemental vitamin D groups (n=31) were dependent on initial levels as serum 25(OH)D (r=-0.63, p<0.05) and 1,25(OH)D (r=-0.45, p<0.05) at Bsl correlated with their increases after supplementation. Supplemental vitamin D increased interferon (IFN)-γ and interleukin (IL)-10 in subjects that were vitamin D insufficient (serum 25(OH)D<29ng/mL) compared to sufficient (serum 25(OH)D⩾30ng/mL) at Bsl. We conclude that supplemental vitamin D increase a pro- and anti-inflammatory cytokine in those with initially low serum 25(OH)D.

Serum cytokines are increased and circulating micronutrients are not altered in subjects with early compared to advanced knee osteoarthritis.

Knee osteoarthritis (OA) is a leading cause of physical disability. At the early stage of knee OA, the increase in synovial fluid cytokine concentrations could contribute to the pathogenesis of OA by degrading articular cartilage. It is unknown, however, if inflammatory cytokines increase systemically at the early or advanced stage of knee OA. The systemic increase of inflammatory cytokines could be detrimental to the endogenous status of micronutrients that protect against excessive inflammation and cytokine-mediated events. The purpose of this study was to test the hypothesis that an increase in serum cytokines associate with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA. Advanced knee OA subjects (n=14) displayed radiographic, pain, and muscular weakness symptoms of knee OA. Early knee OA subjects (n=14) were matched (age, gender, and body mass index) to the advanced OA group and displayed one or two of the aforementioned symptoms of knee OA. Inflammatory cytokines, vitamins C (ascorbic acid), D (25-hydroxyvitamin D), and E (α- and γ-tocopherols), and ß-carotene were measured in fasting blood samples. In the early OA group, serum tumor necrosis factor (TNF)-α, interleukin (IL)-5, IL-6, IL-12, and IL-13 concentrations were significantly (all p<0.05) increased. Circulating ascorbic acid, 25-hydroxyvitamin D, α- and γ-tocopherol's, and ß-carotene concentrations were not significantly different between groups. Based on these preliminary results, we conclude that the systemic increase of inflammatory cytokines is not associated with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA.

Vitamin D deficiency associates with γ-tocopherol and quadriceps weakness but not inflammatory cytokines in subjects with knee osteoarthritis.

Knee osteoarthritis (OA) is a degenerative joint condition and a leading cause of physical disability in the United States. Quadriceps weakness and inflammatory cytokines contribute to the pathogenesis of knee OA, and both of which, increase with vitamin D deficiency. Other micronutrients, such as vitamins C and E and ß-carotene, modulate inflammatory cytokines and decrease during inflammation. The purpose of this study was to test the hypothesis that vitamin D deficiency associates with quadriceps weakness, an increase in serum cytokines, and a decrease in circulating micronutrients in subjects with knee OA. Subjects (age, 48±1 y; serum 25(OH)D, 25.8±1.1 ng/mL) with knee OA were categorized as vitamin D deficient (n=17; serum 25(OH)D≤20 ng/mL), insufficient (n=21; serum 25(OH)D 20-29 ng/mL), or sufficient (n=18; serum 25(OH)D≥30 ng/mL). Single-leg strength (concentric knee extension-flexion contraction cycles at 60 °/s) and blood cytokine, carotene (α and ß), ascorbic acid, and tocopherol (α and γ) concentrations were measured. Quadriceps peak torque, average power, total work, and deceleration were significantly (all p<0.05) impaired with vitamin D deficiency. Serum γ-tocopherol concentrations were significantly (p<0.05) increased with vitamin D deficiency. In the vitamin D sufficient group, γ-tocopherol inversely correlated (r=-0.47, p<0.05) with TNF-α, suggesting a pro-inflammatory increase with a γ-tocopherol decrease despite a sufficient serum 25(OH)D concentration. We conclude that vitamin D deficiency is detrimental to quadriceps function, and in subjects with vitamin D sufficiency, γ-tocopherol could have an important anti-inflammatory role in a pathophysiological condition mediated by inflammation.

Vitamin D sufficiency associates with an increase in anti-inflammatory cytokines after intense exercise in humans.

The purpose of this study was to identify the influence of vitamin D status (insufficient vs. sufficient) on circulating cytokines and skeletal muscle strength after muscular injury. To induce muscular injury, one randomly selected leg (SSC) performed exercise consisting of repetitive eccentric-concentric contractions. The other leg served as the control. An averaged serum 25(OH)D concentration from two blood samples collected before exercise and on separate occasions was used to establish vitamin D insufficiency (<30ng/mL, n=6) and sufficiency (>30ng/mL, n=7) in young, adult males. Serum cytokine concentrations, single-leg peak isometric force, and single-leg peak power output were measured before and during the days following the exercise protocol. The serum IL-10 and IL-13 responses to muscular injury were significantly (both p<0.05) increased in the vitamin D sufficient group. The immediate and persistent (days) peak isometric force (p<0.05) and peak power output (p<0.05) deficits in the SSC leg after the exercise protocol were not ameliorated with vitamin D sufficiency. We conclude that vitamin D sufficiency increases the anti-inflammatory cytokine response to muscular injury.

Pro-inflammatory cytokines mediate the decrease in serum 25(OH)D concentrations after total knee arthroplasty?

Vitamin D is a fat-soluble micronutrient that regulates inflammation and skeletal muscle size and function. Inflammation and skeletal muscle dysfunction (i.e., atrophy and weakness) are predominant impairments that continue to challenge the rehabilitation from total knee arthroplasty (TKA). Data suggest a decrease in serum 25-hydroxyvitamin D (25(OH)D) concentrations after TKA. Despite the decrease being attributed to a systemic inflammatory response, it is unclear what inflammatory mediator(s) is contributing to the decrease in serum 25(OH)D concentrations after TKA. In immune cells, pro-inflammatory cytokines mediate the enzymatic conversion of 25(OH)D to 1,25-dihydroxyvitamin D, implying that pro-inflammatory cytokines contribute to the decrease in substrate availability (i.e., 25(OH)D). We propose the hypothesis that pro-inflammatory cytokines mediate the decrease in serum 25(OH)D concentrations after TKA. To complement the supporting literature for the proposed hypothesis, we analyzed serum 25(OH)D and pro-inflammatory cytokine concentrations prior to and serially after TKA in a case subject (female; age, 62 year; height, 160 cm; body mass, 63 kg; body mass index, 26.5 kg/m(2)). The subtle decrease (12%) from pre-surgery to 2-d post-surgery and the more pronounced decrease (74%) from 3-week to 8-week post-surgery in serum 25(OH)D concentrations corresponded with the increase in serum pro-inflammatory cytokine (i.e., TNF-α, IFN-γ, IL-1ß, GM-CSF, and IL-6) concentrations. This observation lends credence to the proposed hypothesis that pro-inflammatory cytokines could contribute to the decrease in serum 25(OH)D concentrations after TKA. Clearly, future research is needed to confirm the proposed hypothesis and to identify if attenuating the decrease in serum 25(OH)D concentrations improves patient outcomes after TKA.

Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise.

BACKGROUND: Serum 25-hydroxyvitamin D (25(OH)D) concentrations associate with skeletal muscle weakness (i.e., deficit in skeletal muscle strength) after muscular injury or damage. Although supplemental vitamin D increases serum 25(OH)D concentrations, it is unknown if supplemental vitamin D enhances strength recovery after a damaging event. METHODS: Reportedly healthy and modestly active (30 minute of continuous physical activity at least 3 time/week) adult males were randomly assigned to a placebo (n = 13, age, 31(5) y; BMI, 26.9(4.2) kg/m2; serum 25(OH)D, 31.0(8.2) ng/mL) or vitamin D (cholecalciferol, 4000 IU; n = 15; age, 30(6) y; BMI, 27.6(6.0) kg/m2; serum 25(OH)D, 30.5(9.4) ng/mL) supplement. Supplements were taken daily for 35-d. After 28-d of supplementation, one randomly selected leg performed an exercise protocol (10 sets of 10 repetitive eccentric-concentric jumps on a custom horizontal plyo-press at 75% of body mass with a 20 second rest between sets) intended to induce muscle damage. During the exercise protocol, subjects were allowed to perform presses if they were unable to complete two successive jumps. Circulating chemistries (25(OH)D and alanine (ALT) and aspartate (AST) aminotransferases), single-leg peak isometric force, and muscle soreness were measured before supplementation. Circulating chemistries, single-leg peak isometric force, and muscle soreness were also measured before (immediately) and after (immediately, 1-h [blood draw only], 24-h, 48-h, 72-h, and 168-h) the damaging event. RESULTS: Supplemental vitamin D increased serum 25(OH)D concentrations (P < 0.05; ≈70%) and enhanced the recovery in peak isometric force after the damaging event (P < 0.05; ≈8% at 24-h). Supplemental vitamin D attenuated (P < 0.05) the immediate and delayed (48-h, 72-h, or 168-h) increase in circulating biomarkers representative of muscle damage (ALT or AST) without ameliorating muscle soreness (P > 0.05). CONCLUSIONS: We conclude that supplemental vitamin D may serve as an attractive complementary approach to enhance the recovery of skeletal muscle strength following intense exercise in reportedly active adults with a sufficient vitamin D status prior to supplementation.

Higher serum 25-hydroxyvitamin D concentrations associate with a faster recovery of skeletal muscle strength after muscular injury.

The primary purpose of this study was to identify if serum 25-hydroxyvitamin D (25(OH)D) concentrations predict muscular weakness after intense exercise. We hypothesized that pre-exercise serum 25(OH)D concentrations inversely predict exercise-induced muscular weakness. Fourteen recreationally active adults participated in this study. Each subject had one leg randomly assigned as a control. The other leg performed an intense exercise protocol. Single-leg peak isometric force and blood 25(OH)D, aspartate and alanine aminotransferases, albumin, interferon (IFN)-γ, and interleukin-4 were measured prior to and following intense exercise. Following exercise, serum 25(OH)D concentrations increased (p < 0.05) immediately, but within minutes, subsequently decreased (p < 0.05). Circulating albumin increases predicted (p < 0.005) serum 25(OH)D increases, while IFN-γ increases predicted (p < 0.001) serum 25(OH)D decreases. Muscular weakness persisted within the exercise leg (p < 0.05) and compared to the control leg (p < 0.05) after the exercise protocol. Serum 25(OH)D concentrations inversely predicted (p < 0.05) muscular weakness (i.e., control leg vs. exercise leg peak isometric force) immediately and days (i.e., 48-h and 72-h) after exercise, suggesting the attenuation of exercise-induced muscular weakness with increasing serum 25(OH)D prior to exercise. Based on these data, we conclude that pre-exercise serum 25(OH)D concentrations could influence the recovery of skeletal muscle strength after an acute bout of intense exercise.

Circulating pro-inflammatory cytokines are elevated and peak power output correlates with 25-hydroxyvitamin D in vitamin D insufficient adults.

The purpose of this study was to identify circulating cytokines, skeletal muscle strength, and peak power output in young adults with contrasting serum 25-hydroxyvitamin D (25(OH)D) concentrations. Serum 25(OH)D, inflammatory cytokines, muscle strength, and peak power output were, therefore, measured in young adults (25-42 years). Data were collected during the winter to avoid the seasonal influence on serum 25(OH)D. After serum 25(OH)D concentration measurements, subjects were separated into one of two groups: (1) vitamin D insufficient [serum 25(OH)D ≤32 ng/mL, n = 14], or (2) vitamin D sufficient [serum 25(OH)D >32 ng/mL, n = 14]. Following group allocation, serum 25(OH)D concentrations were significantly (p < 0.05) lower and pro-inflammatory cytokines [interleukin (IL)-2, IL-1ß, tumor necrosis factor-α, and interferon-γ] were significantly (all p < 0.05) greater in vitamin D insufficient adults. An anti-inflammatory cytokine (i.e., IL-10; p > 0.05), peak isometric forces (p > 0.05), and peak power outputs (p > 0.05) were not significantly different between vitamin D groups. However, peak power outputs correlated with serum 25(OH)D concentrations in vitamin D insufficient (r = 0.55, p < 0.05) but not in vitamin D sufficient adults (r = -0.27, p = 0.36). Based on these data, we conclude that vitamin D insufficiency, in part, could result in pro-inflammatory stress without altering muscular strength or function in young adults. Future research investigating the causality of the correlation between low-serum 25(OH)D and peak power output in young adults is required.

Different doses of supplemental vitamin D maintain interleukin-5 without altering skeletal muscle strength: a randomized, double-blind, placebo-controlled study in vitamin D sufficient adults.

BACKGROUND: Supplemental vitamin D modulates inflammatory cytokines and skeletal muscle function, but results are inconsistent. It is unknown if these inconsistencies are dependent on the supplemental dose of vitamin D. Therefore, the purpose of this study was to identify the influence of different doses of supplemental vitamin D on inflammatory cytokines and muscular strength in young adults. METHODS: Men (n = 15) and women (n = 15) received a daily placebo or vitamin D supplement (200 or 4000 IU) for 28-d during the winter. Serum 25-hydroxyvitamin D (25(OH)D), cytokine concentrations and muscular (leg) strength measurements were performed prior to and during supplementation. Statistical significance of data were assessed with a two-way (time, treatment) analysis of variance (ANOVA) with repeated measures, followed by a Tukey's Honestly Significant Difference to test multiple pairwise comparisons. RESULTS: Upon enrollment, 63% of the subjects were vitamin D sufficient (serum 25(OH)D ≥ 30 ng/ml). Serum 25(OH)D and interleukin (IL)-5 decreased (P < 0.05) across time in the placebo group. Supplemental vitamin D at 200 IU maintained serum 25(OH)D concentrations and increased IL-5 (P < 0.05). Supplemental vitamin D at 4000 IU increased (P < 0.05) serum 25(OH)D without altering IL-5 concentrations. Although serum 25(OH)D concentrations correlated (P < 0.05) with muscle strength, muscle strength was not changed by supplemental vitamin D. CONCLUSION: In young adults who were vitamin D sufficient prior to supplementation, we conclude that a low-daily dose of supplemental vitamin D prevents serum 25(OH)D and IL-5 concentration decreases, and that muscular strength does not parallel the 25(OH)D increase induced by a high-daily dose of supplemental vitamin D. Considering that IL-5 protects against viruses and bacterial infections, these findings could have a broad physiological importance regarding the ability of vitamin D sufficiency to mediate the immune systems protection against infection.

Fluctuations in the skeletal muscle power-velocity relationship and interferon-γ after a muscle-damaging event in humans.

BACKGROUND: Skeletal muscle power is velocity-dependent under constant load conditions. Interferon (IFN)-γ is an inflammatory cytokine that regulates skeletal muscle recovery following insult in experimental animals. It is unknown if the power-velocity relationship and IFN-γ are modulated after a muscle-damaging event in humans. Therefore, the purpose of this study was to identify the power-velocity relationship and circulating IFN-γ concentration responses to a muscle-damaging event in humans. METHODS: Nine healthy males participated in this study. Each subject had one leg randomly assigned as the control leg. The other leg served as the treatment leg and performed an intense-stretch-shortening cycling (SSC) exercise protocol to induce muscle damage. To measure muscle damage and the power-velocity relationship, unilateral peak isometric force and power output (forces and velocities) measurements were performed prior to, immediately after, and during the days following the SSC protocol. The circulating IFN-γ concentrations were measured in serum samples obtained prior to, immediately after, and during the days following the SSC protocol. Statistical significance of single-leg isometric force and power output data were assessed using a two-way (time and leg treatment) analysis of variance (ANOVA) with repeated measures, followed by a Tukey's honestly significant difference (HSD) to test multiple pairwise comparisons. The statistical significance of the IFN-γ data were assessed using a one-way (time) ANOVA with repeated measures, followed by a Tukey's HSD to test multiple pairwise comparisons. RESULTS: In the treatment leg, significant (P < 0.05) peak isometric force deficits occurred immediately and persisted several days after the SSC protocol, thereby identifying muscle damage-induced weakness. During muscle weakness in the treatment leg, peak power was significantly (P < 0.05) depressed and the velocities at peak power were significantly (P < 0.05) slower. Interestingly, circulating IFN-γ concentrations decreased at 2 and 3 days after compared to those immediately following the SSC protocol. CONCLUSION: We conclude that the velocity to achieve a compromised peak power is reduced, and speculatively, the circulating IFN-γ excursion could be influential on the recovery of skeletal muscle after a muscle-damaging event in humans.