Development and Feasibility of an eHealth Diabetes Prevention Program Adapted for Older Adults-Results from a Randomized Control Pilot Study

Lifestyle programs that reduce health risks and support weight loss (WL) in older adults face adherence and attendance challenges due to reduced energy requirements, impaired mobility, lack of transportation, and low social support. Tailored lifestyle and weight management programs are needed to better support healthy aging for older adults. Here, we developed and piloted an age-adapted, remotely delivered modification of the Diabetes Prevention Program (DPP). The modification includes age-appropriate goals, visuals, and examples; flexible dietary composition; remote classroom and fitness-monitoring technology; and standardized online classroom materials employing pedagogical and behavior change theory. The modifications were designed to safeguard fidelity and to boost adherence, engagement, and knowledge integration, with the convenience of a fully remote WL program for diverse older adults. Six-month pilot data are presented from older adults (55-85 years, body mass index (BMI) 27-39.9 kg/m2, N = 20) randomly allocated to an online DPP intervention with weight, diet, and activity monitored remotely, or into a waitlisted control. The intervention achieved 100% attendance and adherence to self-monitoring. The intervention group mean (±SD) body weight change was -9.5% (±4.1); 90% lost ≥ 5%. By contrast, the control group gained 2.4% (±1.8). Once thought incompatible with older adults, remote interventions are feasible for older adults and can support fidelity, adherence, engagement, and clinically significant WL. Standardized materials are provided for future implementation.

An Overlooked Medication-Induced Celiac Flare Complicating Treatment of Osteoporosis

Background/Objective

Celiac disease, an immune reaction to gluten causing nutrient malabsorption, and long-term glucocorticoid therapy adversely affect bone metabolism and increase fracture risk.

Case Report

A patient with long-standing celiac disease on a strict gluten-free diet and long-term glucocorticoid therapy status post kidney transplant for Sjögren syndrome-induced interstitial nephritis presented for management of osteoporosis. Initial evaluation was notable for secondary hyperparathyroidism, which resolved after switching to a gluten-free calcium citrate supplement. Given normal serum total alkaline phosphatase (ALP) and parathyroid hormone (PTH), she began treatment of osteoporosis with abaloparatide. Two months later, she reported abrupt onset of diarrhea with significant weight loss. Biochemical investigation revealed a threefold increase in serum ALP level. As a precaution, abaloparatide was suspended, yet symptoms persisted with elevated ALP and PTH levels. Endoscopy revealed a celiac flare. The clinic-based pharmacist found that her pharmacy had inadvertently dispensed prednisone tablets containing wheat starch. A switch to a gluten-free formulation led to rapid resolution of the diarrhea with weight regain. Serum ALP and PTH levels normalized, and abaloparatide was resumed without biochemical abnormalities.

Discussion

An unintended switch to a gluten-containing prednisone formulation resulted in uncontrolled celiac disease causing calcium malabsorption, secondary hyperparathyroidism, elevated ALP levels, and an interruption in osteoporosis therapy. Common supplements and drugs can be a hidden source of gluten. Collaboration with a clinic-based pharmacist enhances the detection and prevention of medication-induced adverse reactions.

Conclusion

This case highlights the importance of a careful review of gluten-containing medications and supplements in patients with celiac disease.

Effect of Anamorelin, a Ghrelin Receptor Agonist, on Muscle and Bone in Adults With Osteosarcopenia

CONTEXT

Anamorelin, a ghrelin receptor agonist known to stimulate the pulsatile release of GH from the pituitary, has the potential to improve musculoskeletal health in adults with osteosarcopenia.

OBJECTIVE

To determine the effect of anamorelin treatment for 1 year on muscle mass and strength and on biochemical markers of bone turnover in adults with osteosarcopenia (OS).

DESIGN

Randomized, placebo-controlled, 1-year anamorelin intervention trial.

SETTING

The Bone Metabolism Laboratory at the USDA Nutrition Center at Tufts University.

PARTICIPANTS

26 men and women, age 50 years and older, with OS.

MAIN OUTCOME MEASURES

Muscle mass by D3-creatine dilution and lean body mass (LBM) and bone mineral density (BMD) by dual-energy X-ray absorptiometry, muscle strength, serum IGF-1, and bone turnover markers, serum procollagen 1 intact N-terminal (P1NP), and C-terminal telopeptide (CTX).

RESULTS

Anamorelin did not have a significant effect on muscle mass or LBM; it significantly increased knee flexion torque at 240°/s by 20% (P = .013) and had a similar nonstatistically significant effect on change in knee extension; it increased bone formation (P1NP) by 75% (P = .006) and had no significant effect on bone resorption (CTX) or BMD. Serum IGF-1 increased by 50% in the anamorelin group and did not change in the placebo group (P = .0001 for group difference).

CONCLUSION

In this pilot study, anamorelin did not significantly alter muscle mass; however, it may potentially improve lower extremity strength and bone formation in addition to increasing circulating IGF-1 levels in adults with OS. Further study of anamorelin in this population is warranted.

Effect of a GH Secretagogue, Anamorelin, on Serum Irisin and Inflammation Levels in Osteosarcopenic Adults

Background

Data suggest an association between GH secretion and circulating levels of the myokine irisin and inflammatory cytokinesIL-6 and high-sensitivity C-reactive protein (hsCRP). The impact of GH secretagogues on these markers is unknown.

Objectives

To determine the effect of treatment with the GH secretagogue anamorelin on 12-month changes in serum irisin, IL-6, and hsCRP levels and to assess whether baseline irisin levels modulate the glycemic response to treatment with anamorelin.

Methods

This is an ancillary study in 26 older adults with osteosarcopenia who participated in a 12-month trial examining the effect of anamorelin 100 mg/day vs placebo on musculoskeletal outcomes. Serum irisin, IL-6, and hsCRP were measured at baseline and 12 months.

Results

Treatment with anamorelin, compared with placebo, did not significantly alter irisin levels [12-month change = 0.50 ± 1.2 (SD) ng/mL in anamorelin group and -0.08 ± 2.3 ng/mL in placebo; P = .191]. Baseline irisin levels were not significantly correlated with 2-month change in fasting glucose levels in the anamorelin group (r = -0.222, P = .46) or the placebo group (r = 0.30, P = .34); however, the slopes of the 2 regression lines describing the relationship by group tended to differ (P = .0547). Anamorelin treatment for 12 months had no significant effect on serum IL-6 or hsCRP levels.

Conclusion

In this small sample of older adults with osteosarcopenia, treatment with the GH secretagogue anamorelin did not significantly alter levels of irisin, IL-6, or hsCRP. Higher baseline irisin levels may attenuate the glycemic response to anamorelin treatment; however, a larger study is needed to confirm this possibility.

An Unusually Prolonged Case of FGF23-mediated Hypophosphatemia Secondary to Ferric Carboxymaltose Use

Ferric carboxymaltose (FCM)-induced hypophosphatemia is seen in up to 75% of patients receiving this therapy for iron deficiency anemia. Hypophosphatemia has been attributed to increased circulating levels of fibroblast growth factor-23 (FGF23), the transcription of which is upregulated in an iron-deficient state. However, hypophosphatemia typically resolves within 12 weeks of FCM administration. Here, we present a case of unusually prolonged hypophosphatemia that developed after treatment with FCM in a 39-year-old female with autosomal dominant polycystic kidney disease (ADPKD) but normal renal function. Workup was significant for low tubular reabsorption of phosphate and inappropriately normal FGF23. Genetic disorders of hypophosphatemia and a FGF23-secreting tumor were ruled out. Treatment with calcitriol was required for nearly 3.5 years. The prolonged hypophosphatemia was attributed to underlying ADPKD because these patients demonstrate inappropriately elevated FGF23 levels for the degree of severity of reduced glomerular filtration rate. However, the stimulus driving FGF23 secretion in these patients is incompletely understood. Elevated FGF23 in the kidney suppresses renal tubular phosphate reabsorption and 1α-hydroxylase activity ultimately leading to hypophosphatemia. We conclude that our patient was at a high risk of developing hypophosphatemia because of underlying ADPKD, and FCM was the likely precipitant to identify this underlying process.

A Randomized Study on the Effect of Dried Fruit on Acid-Base Balance, Diet Quality, and Markers of Musculoskeletal Health in Community Dwelling Adults

OBJECTIVES

We tested whether 100 g/day of dried fruit (vs. no supplemental fruit control) for 6 months alters 24-hr urinary net acid excretion (NAE), bone resorption, weight, body composition, muscle performance, and diet quality. We explored consistency of self-selected dietary composition and potential renal acid load (PRAL).

METHODS

This randomized, single-blind, 2-armed study included 83 normal- and over-weight men and postmenopausal women (age ≥50 years) on self-reported low fruit diets. Endpoints included group differences in NAE (primary), 24-hr urinary N-telopeptide (NTX), weight, body composition, muscle performance, and diet quality.

RESULTS

At baseline, mean (±SD) age was 69 ± 8 years; 86% were Caucasian; body mass index was 24.5 ± 2.8 kg/m²; 46% female, and NAE was 32.4 ± 23.1 mmol with no significant baseline group differences. No significant group differences were noted in NAE (primary), NTX, weight, body composition, muscle performance or diet quality at 6 months. In the cohort as a whole, 6-month change in NAE was positively associated with change in NTX, but no significant associations were noted in other outcomes. PRAL on the day of the urine collection was positively associated with NAE. Comparison of two consecutive baseline 24-hr diet recalls revealed wide intra-individual variability in PRAL in self-selected diets in our participants.

CONCLUSION

In this field study of older adults consuming self-selected diets, making one change to the diet by adding 100 g/day of dried fruit (equivalent to 4 servings per day) had no significant impact on NAE when compared to a no supplemental fruit control. This null finding may be attributable to the high day-to-day variability in consumption of foods affecting NAE. Added fruit also had no significant effect on weight, fat, muscle, or bone outcomes over a 6-month period.

Effect of vitamin D supplementation on circulating fibroblast growth factor-23 concentration in adults with prediabetes

BACKGROUND

Recent meta-analyses report that vitamin D supplementation increases blood fibroblast growth factor-23 (FGF23) level.

OBJECTIVES

To determine the effect of 4000 IU/day of vitamin D₃ for 12 months on circulating FGF23 levels. We also examined the association of the achieved 25-hydroxyvitamin D level [25(OH)D] with the FGF23 level at 12 months and with 12-month changes in FGF23.

METHODS

An ancillary analysis among adults 70 years and older with prediabetes who participated in a trial comparing vitamin D₃ 4000 IU/day with placebo. Plasma intact FGF23 and serum 25(OH)D were measured at baseline and month 12 (M12).

RESULTS

Characteristics of the 52 participants (vitamin D₃ n = 28; placebo n = 24) did not differ significantly aside from more women than men in the vitamin D₃ group. Mean ± SD age was 73.8 ± 3.7 years, BMI 31.3 ± 4.2 kg/m2, and glomerular filtration rate (GFR) 76.3 ± 11.8 mL/min/1.73m² Baseline serum 25(OH)D level was 33.4 ± 10.8 ng/mL and increased at M12 to 54.9 ± 14.8 ng/mL in the vitamin D₃ group versus 33.4 ± 14.9 in the placebo (p < 0.001). At baseline, GFR was inversely associated with FGF23 (r = - 0.349, p = 0.011). Change in FGF23 level at M12 did not differ significantly between vitamin D₃ and placebo. In all participants combined, the achieved serum 25(OH)D level at M12 was not significantly associated with the M12 plasma FGF23 or the M12 change in FGF23.

CONCLUSION

In obese older adults with sufficient vitamin D status and normal renal function, vitamin D₃ 4000 IU/day for 12 months did not significantly alter plasma intact FGF23 levels.

CLINICALTRIALS

gov NCT 01,942,694, registered 9/16/2013.

Randomized controlled trial of a novel lifestyle intervention used with or without meal replacements in work sites

OBJECTIVE

Lifestyle interventions have had limited effectiveness in work sites when evaluated in randomized trials. This study assessed the effectiveness of a novel lifestyle intervention for weight loss (Healthy Weight for Living [HWL]) implemented with or without meal replacements (MR) in work sites. HWL used a new behavioral approach emphasizing reducing hunger and building healthy food preferences, and, unlike traditional lifestyle interventions, it did not require calorie counting.

METHODS

Twelve work sites were randomized to an 18-month intervention (n = 8; randomization within work sites to HWL, HWL + MR) or 6-month wait-listed control (n = 4). Participants were employees with overweight or obesity (N = 335; age = 48 [SD 10] years; BMI = 33 [6] kg/m2 ; 83% female). HWL was group-delivered in person or by videoconference. The primary outcome was 6-month weight change; secondary outcomes included weight and cardiometabolic risk factors measured at 6, 12, and 18 months in intervention groups.

RESULTS

Mean 6-month weight change was -8.8% (95% CI: -11.2% to -6.4%) for enrollees in HWL and -8.0% (-10.4% to -5.5%) for HWL + MR (p < 0.001 for both groups vs. controls), with no difference between interventions (p = 0.40). Clinically meaningful weight loss (≥5%) was maintained at 18 months in both groups (p < 0.001).

CONCLUSIONS

A new lifestyle intervention approach, deliverable by videoconference with or without MR, supported clinically impactful weight loss in employees.

Effect of vitamin D3 vs. calcifediol on VDR concentration and fiber size in skeletal muscle

INTRODUCTION

This study sought to examine the effect of vitamin D₃ (VD₃) 3200 IU/d, calcifediol (HyD) 20mcg/d, or placebo on intramyonuclear vitamin D receptor (VDR) concentration, muscle fiber cross-sectional area (FCSA), and muscle satellite cell activation.

MATERIALS AND METHODS

It was conducted on a subset of the VD₃ (n = 12), HyD (n = 11), and placebo (n = 13) groups who participated in the 6-month randomized controlled HyD Osteopenia Study in postmenopausal women. Baseline and 6-month vastus lateralis muscle cross sections were probed for VDR, fiber type I and II, and PAX7 (satellite cell marker) using immunofluorescence.

RESULTS

Baseline mean ± SD age was 61 ± 4 years and serum 25-hydroxyvitamin D (25OHD) level was 55.1 ± 22.8 nmol/L. Baseline characteristics did not differ significantly by group. Six-month mean ± SD 25OHD levels were 138.7 ± 22.2 nmol/L (VD₃), 206.8 ± 68.8 nmol/L (HyD), and 82.7 ± 36.1 nmol/L (placebo), ANOVA P < 0.001. There were no significant group differences in 6-month change in VDR concentration (ANOVA P = 0.227). Mean ± SD percent 6-month changes in type I FCSA were 20.5 ± 32.7% (VD₃), - 6.6 ± 20.4% (HyD), and - 0.3 ± 14.0% (placebo, ANOVA P = 0.022). Type II FCSA or PAX7 concentration did not change significantly by group (all P > 0.358).

CONCLUSION

This study demonstrated no significant change in intramyonuclear VDR in response to either form of vitamin D vs. placebo. Type I FCSA significantly increased with VD₃, but not with HyD at 6 months. As type I fibers are more fatigue resistant than type II, enlargement in type I suggests potential for improved muscle endurance. Although HyD resulted in the highest 25OHD levels, no skeletal muscle benefits were noted at these high levels.

CLINICAL TRIAL

NCT02527668.

Effects of Vitamin D with Calcium and Associations of Mean 25-Hydroxyvitamin D Levels with 3-Year Change in Muscle Performance in Healthy Older Adults in the Boston STOP IT Trial

The purpose of this analysis was to assess whether (1) daily vitamin D₃ plus calcium supplementation vs. placebo or (2) the mean 25-hydroxyvitamin D [25(OH)D] level achieved during a 3-year trial was associated with muscle performance or balance in the Boston STOP IT study. Methods We conducted exploratory analyses in 386 men and women age 65 years and older who participated in the Boston STOP IT trial and had one or more muscle performance or balance assessments at baseline and 3 years. Participants were treated with 700 IU of vitamin D₃ plus 500 mg of calcium or with double placebo daily for 3 years. Plasma 25(OH)D was measured at baseline, 6, 12, 18, 24, and 36 months; muscle performance (timed walk, grip strength, and chair-rise) and two balance tests, the one-leg stand and tandem stand, were assessed at baseline and 3 years only. Results Supplementation with vitamin D3 and calcium had no favorable effect on any muscle performance measure. The 3-year mean 25(OH)D levels were 22.7 ± 6.3 (SD) in the placebo and 30.8 ± 7.5 ng/ml in the supplemented groups (p < 0.001). The 3-year mean 25(OH)D level was positively associated with change in one-leg stand time (p = 0.04), but not with the other measures. Conclusion Vitamin D3 and calcium supplementation had no favorable effect on muscle performance or balance in this relatively healthy older population. A higher 3-year mean 25(OH)D level may favor balance, as indicated by longer one-leg stand time, but this observation should be confirmed.

Intra-trial Mean 25(OH)D and PTH Levels and Risk of Falling in Older Men and Women in the Boston STOP IT Trial

CONTEXT

Supplementation with vitamin D has the potential to both reduce and increase risk of falling, and parathyroid hormone (PTH) may contribute to fall risk.

OBJECTIVE

To assess the associations of intra-trial mean circulating levels of 25-hydroxyvitamin D [25(OH)D] and PTH on incident falls in healthy older adults.

DESIGN

Observational within a clinical trial.

SETTING

The Bone Metabolism Laboratory at the USDA Nutrition Center at Tufts University.

PARTICIPANTS

410 men and women age ≥65 years who participated in the 3-year Boston STOP IT trial to determine the effect of supplementation with 700 IU of vitamin D3 plus calcium on incident falls (secondary endpoint). Intra-trial exposures of 25(OH)D and PTH were calculated as the mean of biannual measures up to and including the first fall.

MAIN OUTCOME MEASURES

Incidence of first fall.

RESULTS

Intra-trial mean 25(OH)D was significantly associated with risk of falling in a U-shaped pattern; the range associated with minimal risk of falling was approximately 20 to 40 ng/mL. PTH was not significantly associated with risk of falling.

CONCLUSIONS

The findings highlight the importance of maintaining the circulating 25(OH)D level between 20 and 40 ng/mL, the range that is also recommended for bone health. At PTH levels within the normal range, there was no detectible independent association of PTH with fall risk.

Effects of Low Doses of L-Carnitine Tartrate and Lipid Multi-Particulate Formulated Creatine Monohydrate on Muscle Protein Synthesis in Myoblasts and Bioavailability in Humans and Rodents

The primary objective of this study was to investigate the potential synergy between low doses of L-carnitine tartrate and creatine monohydrate to induce muscle protein synthesis and anabolic pathway activation in primary human myoblasts. In addition, the effects of Lipid multi-particulates (LMP) formulation on creatine stability and bioavailability were assessed in rodents and healthy human subjects. When used individually, L-carnitine tartrate at 50 µM and creatine monohydrate at 0.5 µM did not affect myoblast protein synthesis and signaling. However, when combined, they led to a significant increase in protein synthesis. Increased AKT and RPS6 phosphorylation were observed with 50 µM L-carnitine tartrate 5 µM creatine in combination in primary human myoblasts. When Wistar rats were administered creatine with LMP formulation at either 21 or 51 mg/kg, bioavailability was increased by 27% based on the increase in the area under the curve (AUC) at a 51 mg/kg dose compared to without LMP formulation. Tmax and Cmax were unchanged. Finally, in human subjects, a combination of LMP formulated L-carnitine at 500 mg (from L-carnitine tartrate) with LMP formulated creatine at 100, 200, or 500 mg revealed a significant and dose-dependent increase in plasma creatine concentrations. Serum total L-carnitine levels rose in a similar manner in the three combinations. These results suggest that a combination of low doses of L-carnitine tartrate and creatine monohydrate may lead to a significant and synergistic enhancement of muscle protein synthesis and activation of anabolic signaling. In addition, the LMP formulation of creatine improved its bioavailability. L-carnitine at 500 mg and LMP-formulated creatine at 200 or 500 mg may be useful for future clinical trials to evaluate the effects on muscle protein synthesis.

A Case of Arrowroot Starch Adulteration: Importance of Independent Testing of Dietary Supplements in Clinical Nutrition Research

Objectives

Adulteration of dietary supplements is widespread and can affect the quality and credibility of clinical nutrition research. In this case report, we describe the difficulties encountered with identity testing of one of our dietary supplements – arrowroot starch – chosen as the placebo for our nutrition intervention trial.

Methods

To test the effect of protein and alkali on skeletal muscle health, we planned a randomized controlled trial using a high protein diet supplement with or without an alkaline salt supplement. The study selected Maranta arundinacea L. (arrowroot) starch as placebo because of its neutral potential renal acid load compared to some other starches. Commercially available samples of arrowroot starch were purchased from three different US distributors. Independent identity testing was conducted by digital microscopy by Alkemist Labs (Garden Grove, CA).

Results

All three commercially available arrowroot starch samples came with an authentication certificate stating that the starch was derived from the Maranta arundinacea L. plant. On gross examination, the appearance, odor, and consistency of all three samples was similar. On microscopy with digital photo documentation, starch granules from the Maranta arundinacea L. plant range in shape from ovoid, pear-shaped to triangular. The expected size would be 40–75 um and the distinct pattern would have concentric striations and a hilum that resembles a bird or “M”. Surprisingly, we found that only one of the three commercially available arrowroot starch samples was characteristic of Maranta arundinacea L. granules on microscopy. The starch granules from samples from the other two US distributors could not be identified.

Conclusions

This case study reveals the extensive adulteration of commercially available arrowroot starch in the US. It also highlights the importance of third-party, independent testing of dietary supplements to confirm authentication of the product composition especially for clinical nutrition trials.

Funding Sources

NIA R01AG055443–03 (Ceglia).

Vitamin D Supplementation and Prevention of Type 2 Diabetes

BACKGROUND

Observational studies support an association between a low blood 25-hydroxyvitamin D level and the risk of type 2 diabetes. However, whether vitamin D supplementation lowers the risk of diabetes is unknown.

METHODS

We randomly assigned adults who met at least two of three glycemic criteria for prediabetes (fasting plasma glucose level, 100 to 125 mg per deciliter; plasma glucose level 2 hours after a 75-g oral glucose load, 140 to 199 mg per deciliter; and glycated hemoglobin level, 5.7 to 6.4%) and no diagnostic criteria for diabetes to receive 4000 IU per day of vitamin D₃ or placebo, regardless of the baseline serum 25-hydroxyvitamin D level. The primary outcome in this time-to-event analysis was new-onset diabetes, and the trial design was event-driven, with a target number of diabetes events of 508.

RESULTS

A total of 2423 participants underwent randomization (1211 to the vitamin D group and 1212 to the placebo group). By month 24, the mean serum 25-hydroxyvitamin D level in the vitamin D group was 54.3 ng per milliliter (from 27.7 ng per milliliter at baseline), as compared with 28.8 ng per milliliter in the placebo group (from 28.2 ng per milliliter at baseline). After a median follow-up of 2.5 years, the primary outcome of diabetes occurred in 293 participants in the vitamin D group and 323 in the placebo group (9.39 and 10.66 events per 100 person-years, respectively). The hazard ratio for vitamin D as compared with placebo was 0.88 (95% confidence interval, 0.75 to 1.04; P = 0.12). The incidence of adverse events did not differ significantly between the two groups.

CONCLUSIONS

Among persons at high risk for type 2 diabetes not selected for vitamin D insufficiency, vitamin D₃ supplementation at a dose of 4000 IU per day did not result in a significantly lower risk of diabetes than placebo. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; D2d ClinicalTrials.gov number, NCT01942694.).

Pilot Study Examining the Influence of Potassium Bicarbonate Supplementation on Nitrogen Balance and Whole-Body Ammonia and Urea Turnover Following Short-Term Energy Restriction in Older Men

With aging there is a chronic low-grade metabolic-acidosis that may exacerbate negative protein balance during weight loss. The objective of this randomized pilot study was to assess the impact of 90 mmol∙day⁻¹ potassium bicarbonate (KHCO₃) versus a placebo (PLA) on 24-h urinary net acid excretion (NAE), nitrogen balance (NBAL), and whole-body ammonia and urea turnover following short-term diet-induced weight loss. Sixteen (KHCO₃; n = 8, PLA; n = 8) older (64 ± 4 years) overweight (BMI: 28.5 ± 2.1 kg∙day⁻¹) men completed a 35-day controlled feeding study, with a 7-day weight-maintenance phase followed by a 28-day 30% energy-restriction phase. KHCO₃ or PLA supplementation began during energy restriction. NAE, NBAL, and whole-body ammonia and urea turnover (¹⁵N-glycine) were measured at the end of the weight-maintenance and energy-restriction phases. Following energy restriction, NAE was −9.8 ± 27.8 mmol∙day⁻¹ in KHCO₃ and 43.9 ± 27.8 mmol∙day⁻¹ in PLA (p < 0.05). No significant group or time differences were observed in NBAL or ammonia and urea turnover. Ammonia synthesis and breakdown tended (p = 0.09) to be higher in KHCO₃ vs. PLA following energy restriction, and NAE was inversely associated (r = −0.522; p < 0.05) with urea synthesis in all subjects. This pilot study suggests some benefit may exist with KHCO₃ supplementation following energy restriction as lower NAE indicated higher urea synthesis.

Increasing alkali supplementation decreases urinary nitrogen excretion when adjusted for same day nitrogen intake

We examined whether escalating doses of potassium bicarbonate (KHCO₃) supplements alter urinary nitrogen excretion expressed as a ratio to same day nitrogen intake (measure of muscle-protein breakdown). The ratio declined significantly from placebo to low to high dose of KHCO₃ supplementation in older adults over 3 months, suggesting muscle-sparing.

INTRODUCTION

Neutralization of dietary acid load with alkali supplementation (i.e., KHCO₃) has been hypothesized to have muscle protein-sparing effects. In controlled feeding studies with fixed nitrogen (N) intake/day, 24-h urinary N excretion is a good marker of muscle breakdown. However, in studies with self-selected diets, changes in 24-h urinary N excretion can be influenced by shifts in N intake.

METHODS

We evaluated changes in 24-h total urinary N excretion as a ratio of N excretion to concurrent N intake in 233 older men and women who participated in an 84-day KHCO₃ supplementation randomized placebo-controlled trial.

RESULTS

After adjustment for relevant cofactors, escalating doses of KHCO₃ (1 mmol/kg/day [low] or 1.5 mmol/kg/day [high]) resulted in a progressive decline in urinary N excretion/N intake compared to placebo (overall P for trend = 0.042). The 84-day change in urinary N excretion/N intake in the high-dose KHCO₃ group was statistically significantly lower compared to placebo (P = 0.012) but not compared to the low-dose KHCO₃ group (P = 0.276). The 84-day change in urinary N excretion/N intake in the low-dose KHCO₃ group did not differ significantly from placebo (P = 0.145).

CONCLUSIONS

Urinary N excretion expressed as ratio to same day N intake declined steadily with increasing doses of KHCO₃ supplementation from low 1 mmol/kg/day to high 1.5 mmol/kg/day, suggesting a nitrogen-sparing effect. Compared to urinary N excretion alone, this ratio could be a more reasonable measure of muscle protein metabolism in large-scale long-term human studies.

TRIAL REGISTRATION

Clinicaltrials.gov NCT1475214.

A likely cranial osteodystrophy (Paget's disease of bone) in a Precolumbian, Mesoamerican stone sculpture

This short note illustrates facial and head features found in a stone sculpture of the ancient, Precolumbian period in a temple of the Mayan city of Copan (Honduras). The authors believe that this observation may support paleoanthropological evidence of Paget's disease of bone, an osteodystrophy described in the Mesoamerican Indian populations before the first millennium A.D.

Upregulation of circulating myomiR following short-term energy restriction is inversely associated with whole body protein synthesis

The objective of the present investigation was to determine whether energy restriction (ER) influences expression of skeletal muscle-specific microRNA (miRNA) in circulation (c-myomiR) and whether changes in c-myomiR are associated with rates of whole body protein synthesis. Sixteen older (64 ± 2 yr) overweight (28.5 ± 1.2 kg/m²) men enrolled in this 35-day controlled feeding trial. A 7-day weight maintenance (WM) period was followed by 28 days of 30% ER. Whole body protein turnover was determined from [¹⁵N]glycine enrichments in 24-h urine collections, and c-myomiR (miR-1-3p, miR-133a-3p, miR-133b, and miR-206) expression was assessed from serum samples by RT-quantitative PCR upon completion of the WM and ER periods. Participants lost 4.4 ± 0.3 kg body mass during ER (P < 0.05). After 28 days of ER, miR-133a and miR-133b expression was upregulated (P < 0.05) compared with WM. When all four c-myomiR were grouped as c-myomiR score (sum of the median fold change of all myomiR), overall expression of c-myomiR was higher (P < 0.05) at ER than WM. Backward linear regression analysis of whole body protein synthesis and breakdown and carbohydrate, fat, and protein oxidation determined protein synthesis to be the strongest predictor of c-myomiR score. An inverse association (P < 0.05) was observed with ER c-myomiR score and whole body protein synthesis (r = -0.729, r² = -0.530). Findings from the present investigation provide evidence that upregulation of c-myomiR expression profiles in response to short-term ER is associated with lower rates of whole body protein synthesis.

Effects of Potassium Bicarbonate Supplements on Circulating microRNA Expression

Several studies suggest that neutralizing acid load in the diet with alkali had favorable effects on intermediate markers of musculoskeletal health. We examined whether alkali supplementation with potassium bicarbonate [(KHCO₃); 81 mmol/d; n = 12] vs placebo (n = 12) for 84 days altered serum microRNAs, potential biomarkers associated with innumerable biological processes including bone and muscle metabolism. Serum microRNAs, urinary net acid excretion (UNAE), urinary N-telopeptide (UNTX), urinary calcium (UCa), urinary nitrogen (UN), glomerular filtration rate, serum procollagen type 1 amino-terminal propeptide (P1NP), serum insulin-like growth factor-1 (IGF-1), and its serum binding protein IGFBP3 were measured at baseline and day 84. Baseline characteristics and measurements were similar in the two treatment groups. Eighty-four-day changes in UNAE differed by group (KHCO₃, -47 ± 9 mmol; placebo, -5 ± 5 mmol; P < 0.01). KHCO₃ significantly reduced UNTX, UCa, and serum P1NP but did not affect UN, serum IGF-1, or IGFBP3 levels compared with placebo over 84 days. Fold change in serum circulating microRNA (c-miR)-133b differed significantly by group (KHCO₃, 2.26 ± 0.85; placebo, -1.23 ± 0.69; P < 0.01); there was a similar trend in c-miR-21-5p. Fold changes in c-miR-133b and c-miR-21-5p were inversely associated with changes in UNAE and UNTX; fold change in c-miR-21-5p was inversely associated with change in UCa, with a similar trend with c-miR-133b. In summary, reducing renal acid load with KHCO₃ was associated with increased expressions of c-miR-133b and c-miR-21-5p. Furthermore, increases in c-miRNA-133b and c-miR-21-5p were inversely associated with bone resorption markers UNTX and UCa consistent with potential beneficial effects on bone in older adults. However, the broader significance of c-miRNAs as musculoskeletal biomarkers is still under investigation, and larger studies are needed to verify these preliminary results.

Potassium Bicarbonate Supplementation Lowers Bone Turnover and Calcium Excretion in Older Men and Women: A Randomized Dose-Finding Trial

The acid load accompanying modern diets may have adverse effects on bone and muscle metabolism. Treatment with alkaline salts of potassium can neutralize the acid load, but the optimal amount of alkali is not established. Our objective was to determine the effectiveness of two doses of potassium bicarbonate (KHCO3 ) compared with placebo on biochemical markers of bone turnover, and calcium and nitrogen (N) excretion. In this double-blind, randomized, placebo-controlled study, 244 men and women age 50 years and older were randomized to placebo or 1 mmol/kg or 1.5 mmol/kg of KHCO3 daily for 3 months; 233 completed the study. The primary outcomes were changes in 24-hour urinary N-telopeptide (NTX) and N; changes in these measures were compared across the treatment groups. Exploratory outcomes included 24-hour urinary calcium excretion, serum amino-terminal propeptide of type I procollagen (P1NP), and muscle strength and function assessments. The median administered doses in the low-dose and high-dose groups were 81 mmol/day and 122 mmol/day, respectively. When compared with placebo, urinary NTX declined significantly in the low-dose group (p = 0.012, after adjustment for baseline NTX, gender, and change in urine creatinine) and serum P1NP declined significantly in the low-dose group (p = 0.004, adjusted for baseline P1NP and gender). Urinary calcium declined significantly in both KHCO3 groups versus placebo (p < 0.001, adjusted for baseline urinary calcium, gender, and changes in urine creatinine and calcium intake). There was no significant effect of either dose of KHCO3 on urinary N excretion or on the physical strength and function measures. KHCO3 has favorable effects on bone turnover and calcium excretion and the lower dose appears to be the more effective dose. Long-term trials to assess the effect of alkali on bone mass and fracture risk are needed.

Vitamin D receptor protein is associated with interleukin-6 in human skeletal muscle

Vitamin D is associated with skeletal muscle physiology and function and may play a role in intramuscular inflammation, possibly via the vitamin D receptor (VDR). We conducted two studies to examine (1) whether serum 25-hydroxyvitamin D (25OHD) and/or intramuscular VDR protein concentrations are associated with intramuscular interleukin-6 (IL-6) and/or tumor necrosis factor-α (TNFα); and (2) whether 16-week supplementation with vitamin D3 alters intramuscular IL-6 and/or TNFα. Potential-related signaling pathways were also examined. Muscle biopsies of 30 older, mobility-limited adults were obtained at baseline. A subset of 12 women were supplemented with either 4,000 IU/day of vitamin D3 (N = 5) or placebo (N = 7), and biopsies were repeated at 16 weeks. Serum 25OHD was measured, and intramuscular VDR, IL-6, and TNFα gene expressions and protein concentrations were analyzed. Baseline serum 25OHD was not associated with intramuscular IL-6 or TNFα gene expression or protein concentration. Baseline intramuscular VDR protein concentration, adjusted for baseline serum 25OHD, was positively associated with intramuscular IL-6 gene expression (n = 28; p = 0.04), but negatively associated with intramuscular IL-6 protein (n = 18; p = 0.03). Neither intramuscular IL-6 nor TNFα gene expression was different between placebo (n = 7) or vitamin D3 supplementation groups (n = 5) after 16 weeks (p = 0.57, p = 0.11, respectively). These data suggest that VDR is a better predictor than serum 25OHD concentration of intramuscular IL-6 gene and protein expressions. A similar relationship was not observed for TNFα expression. Further, supplementation with 4,000 IU vitamin D3 per day does not appear to affect intramuscular IL-6 or TNFα gene expression after 16 weeks.

Post-thyroidectomy hypocalcemia exacerbated by chyle leak

Transient hypocalcemia after thyroidectomy is not uncommon and the risk increases with the extent of neck surgery. We report a case of severe and prolonged hypocalcemia after total thyroidectomy complicated by thoracic duct injury. Hypoparathyroidism and thoracic duct injury are potential complications following total thyroidectomy with extensive lymph node dissection. This case suggested that having both conditions may complicate treatment of hypoparathyroid-induced hypocalcemia by way of losses of calcium and vitamin D in the chyle leak.

Effects of 1,25-dihydroxyvitamin D3 and vitamin D3 on the expression of the vitamin d receptor in human skeletal muscle cells

Vitamin D receptor (VDR) expression and action in non-human skeletal muscle have recently been reported in several studies, yet data on the activity and expression of VDR in human muscle cells are scarce. We conducted a series of studies to examine the (1) effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on VDR gene expression in human primary myoblasts, (2) effect of 16-week supplementation with vitamin D3 on intramuscular VDR gene expression in older women, and (3) association between serum 25-hydroxyvitamin D (25OHD) and intramuscular VDR protein concentration in older adults. Human primary myoblasts were treated with increasing concentrations of 1,25(OH)2D3 for 18 h. A dose-dependent treatment effect was noted with 1 nmol/L of 1,25OH2D3 increasing intramuscular VDR mRNA expression (mean fold change±SD 1.36±0.33; P=0.05). Muscle biopsies were obtained at baseline and 16 weeks after vitamin D3 supplementation (4,000 IU/day) in older adults. Intramuscular VDR mRNA was significantly different from placebo after 16 weeks of vitamin D3 (1.2±0.99; -3.2±1.7, respectively; P=0.04). Serum 25OHD and intramuscular VDR protein expression were examined by immunoblot. 25OHD was associated with intramuscular VDR protein concentration (R=0.67; P=0.0028). In summary, our study found VDR gene expression increases following treatment with 1,25OH2D3 in human myoblasts. 25OHD is associated with VDR protein and 16 weeks of supplementation with vitamin D3 resulted in a persistent increase in VDR gene expression of vitamin D3 in muscle tissue biopsies. These findings suggest treatment with vitamin D compounds results in sustained increases in VDR in human skeletal muscle.

The emerging biomolecular role of vitamin D in skeletal muscle

In this review, we summarize current evidence for a direct effect of vitamin D on skeletal muscle. A number of studies identify the receptor for 1,25-dihydroxyvitamin-D3 (vitamin D receptor (VDR)) and the enzyme CYP27B1 (1-α-hydroxylase) in muscle. We hypothesize that vitamin D acts on myocytes via the VDR, and we examine proposed effects on myocyte proliferation, differentiation, growth, and inflammation.

Effect of supplemental vitamin D and calcium on serum sclerostin levels

OBJECTIVE

Serum sclerostin levels have been reported to be inversely associated with serum 25OHD levels, but the effect of vitamin D and calcium supplementation on serum sclerostin levels is unknown. This study was carried out to determine whether vitamin D and calcium supplementation altered serum sclerostin levels in healthy older adults.

DESIGN

We measured serum sclerostin levels at baseline and after 2 years in 279 men and women who participated in a placebo-controlled vitamin D (700 IU/day) and calcium (500 mg/day) intervention trial carried out in men and women aged ≥65 years.

METHOD

Serum sclerostin levels were measured using the MesoScale Discovery chemiluminescence assay.

RESULTS

In the men, sclerostin levels increased over 2 years by 4.11±1.81 ng/l (13.1%) in the vitamin D plus calcium-supplemented group and decreased by 3.16±1.78 ng/l (10.9%) in the placebo group (P=0.005 for difference in change). Adjustments for the season of measurement, baseline physical activity levels, baseline serum sclerostin levels, and total body bone mineral content did not substantially alter the changes. In the women, there was no significant group difference in change in serum sclerostin levels either before or after the above-mentioned adjustments. In both the sexes, vitamin D and calcium supplementation significantly increased serum ionized calcium levels and decreased parathyroid hormone levels.

CONCLUSION

Men and women appear to have different serum sclerostin responses to vitamin D and calcium supplementation. The reason for this difference remains to be determined.

Serum sclerostin levels vary with season

CONTEXT

To establish the clinical utility of serum sclerostin levels, it is important to know whether there is seasonal variation in the measurements.

OBJECTIVE

This study was done to determine whether serum sclerostin levels vary by season in healthy older men and women.

METHODS

Serum sclerostin levels were measured in archived serum of 314 healthy men and women aged 65 years and older and examined for seasonal variation. Several factors known to vary by season and previously reported to be associated with serum sclerostin levels, including serum osteocalcin, physical activity, and serum PTH levels, were also measured in these subjects. Sex did not modify the association of season with sclerostin, so the men and women were analyzed together.

RESULTS

Serum sclerostin levels varied significantly by season (P < .001, after adjustment for sex). Sclerostin levels in the wintertime were 20% higher than the all-year mean, the levels gradually declined through the spring and summer, and by the fall, they were 20% below the all-year mean. Adjustment for serum osteocalcin, physical activity, and serum PTH did not alter the seasonal means. Seasonal differences in serum osteocalcin, physical activity, and serum PTH were not statistically significant.

CONCLUSIONS

This study documents marked seasonal variation in serum sclerostin levels. It is important to recognize this source of biological variability when considering the potential clinical utility of sclerostin measurements.

A randomized study on the effect of vitamin D₃ supplementation on skeletal muscle morphology and vitamin D receptor concentration in older women

CONTEXT

Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor (VDR) concentration are lacking.

OBJECTIVE

Our objective was to determine whether vitamin D₃ 4000 IU/d alters muscle fiber cross-sectional area (FCSA) and intramyonuclear VDR concentration over 4 months.

DESIGN AND SETTING

This was a randomized, double-blind, placebo-controlled study in a single center.

PARTICIPANTS

Participants were 21 mobility-limited women (aged ≥ 65 years) with serum 25-hydroxyvitamin D (25OHD) levels of 22.5 to 60 nmol/L.

MAIN OUTCOME MEASURES

Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type (I/IIa/IIx) and VDR using immunofluorescence.

RESULTS

At baseline, mean (±SD) age was 78 ± 5 years; body mass index was 27 ± 5 kg/m², 25OHD was 46.3 ± 9.5 nmol/L, and a short physical performance battery score was 7.95 ± 1.57 out of 12. At 4 months, 25OHD level was 52.5 ± 17.1 (placebo) vs 80.0 ± 11.5 nmol/L (vitamin D [VD]; P < .01), and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group (r = 0.87, P < .001). By treatment group, percent change in intramyonuclear VDR concentration was 7.8% ± 18.2% (placebo) vs 29.7% ± 11.7% (VD; P = .03) with a more pronounced group difference in type II vs I fibers. Percent change in total (type I/II) FCSA was -7.4% ± 18.9% (placebo) vs 10.6% ± 20.0% (VD; P = .048).

CONCLUSION

Vitamin D₃ supplementation increased intramyonuclear VDR concentration by 30% and increased muscle fiber size by 10% in older, mobility-limited, vitamin D-insufficient women. Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved.

Effects of alkali supplementation and vitamin D insufficiency on rat skeletal muscle

Data on the independent and potential combined effects of acid-base balance and vitamin D status on muscle mass and metabolism are lacking. We investigated whether alkali supplementation with potassium bicarbonate (KHCO3), with or without vitamin D3 (± VD3), alters urinary nitrogen (indicator of muscle proteolysis), muscle fiber cross-sectional area (FCSA), fiber number (FN), and anabolic (IGF-1, Akt, p70s6k) and catabolic (FOXO3a, MURF1, MAFbx) signaling pathways regulating muscle mass. Thirty-six, 20-month-old, Fischer 344/Brown-Norway rats were randomly assigned in a 2 × 2 factorial design to one of two KHCO3-supplemented diets (± VD3) or diets without KHCO3 (± VD3) for 12 weeks. Soleus, extensor digitorum longus (EDL), and plantaris muscles were harvested at 12 weeks. Independent of VD3 group, KHCO3 supplementation resulted in 35 % lower mean urinary nitrogen to creatinine ratio, 10 % higher mean type I FCSA (adjusted to muscle weight), but no statistically different mean type II FCSA (adjusted to muscle weight) or FN compared to no KHCO3. Among VD3-replete rats, phosphorylated-Akt protein expression was twofold higher in the KHCO3 compared to no KHCO3 groups, but this effect was blunted in rats on VD3-deficient diets. Neither intervention significantly affected serum or intramuscular IGF-1 expression, p70s6k or FOXO3a activation, or MURF1 and MAFbx gene expression. These findings provide support for alkali supplementation as a promising intervention to promote preservation of skeletal muscle mass, particularly in the setting of higher vitamin D status. Additional research is needed in defining the muscle biological pathways that are being targeted by alkali and vitamin D supplementation.

Meal conditions affect the absorption of supplemental vitamin D3 but not the plasma 25-hydroxyvitamin D response to supplementation

It is sometimes assumed that dietary fat is required for vitamin D absorption, although the impact of different amounts of dietary fat on vitamin D absorption is not established. This study was conducted to determine whether the presence of a meal and the fat content of the meal influences vitamin D absorption or the 25-hydroxyvitamin D [25(OH)D] response to supplemental vitamin D3 . Based on earlier studies in rats we postulated that absorption would be greatest in the low-fat meal group. Sixty-two healthy older men and women were randomly assigned to one of three meal groups: no meal, high-fat meal, or low-fat meal; each was given a monthly 50,000 IU vitamin D3 supplement with the test breakfast meal (or after a fast for the no-meal group) and followed for 90 days. Plasma vitamin D3 was measured by liquid chromatography-mass spectroscopy (LC/MS) before and 12 hours after the first dose; plasma 25(OH)D was measured by radioimmunoassay at baseline and after 30 and 90 days. The mean 12-hour increments in vitamin D3 , after adjusting for age and sex, were 200.9 nmol/L in the no-meal group, 207.4 nmol/L in the high-fat meal group, and 241.1 nmol/L in the low-fat meal group (p = 0.038), with the increase in the low-fat group being significantly greater than the increases in the other two groups. However, increments in 25(OH)D levels at 30 and 90 days did not differ significantly in the three groups. We conclude that absorption was increased when a 50,000 IU dose of vitamin D was taken with a low-fat meal, compared with a high-fat meal and no meal, but that the greater absorption did not result in higher plasma 25(OH)D levels in the low-fat meal group.

Vitamin D and its role in skeletal muscle

This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated with risk of falling. Clinical trials of vitamin D supplementation in older adults with low vitamin D status mostly report improvements in muscle performance and reductions in falls. The underlying mechanisms are probably both indirect via calcium and phosphate and direct via activation of the vitamin D receptor (VDR) on muscle cells by 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. VDR activation at the genomic level regulates transcription of genes involved in calcium handling and muscle cell differentiation and proliferation. A putative membrane-associated VDR activates intracellular signaling pathways also involved in calcium handling and signaling and myogenesis. Additional evidence comes from VDR knockout mouse models with abnormal muscle morphology and physical function, and VDR polymorphisms which are associated with differences in muscle strength. Recent identification of CYP27B1 bioactivity in skeletal muscle cells and in regenerating adult mouse muscle lends support to the direct action of both 25-hydroxyvitamin D and 1,25(OH)(2)D in muscle. Despite these research advances, many questions remain. Further research is needed to fully characterize molecular mechanisms of vitamin D action on muscle cells downstream of the VDR, describe the effects on muscle morphology and contractility, and determine whether these molecular and cellular effects translate into clinical improvements in physical function.

Serum 25-hydroxyvitamin D concentration and physical function in adult men

OBJECTIVE

Recent reports suggest that vitamin D status influences musculoskeletal health; yet, there are limited data in adult men. This study investigated whether serum 25-hydroxyvitamin D [25(OH)D] concentration was associated with lean body mass, muscle strength and physical performance in men.

DESIGN

Population-based, observational survey.

PARTICIPANTS

1219 black, Hispanic and white randomly selected men aged 30-79 years from the Boston Area Community Health/Bone Survey.

MEASUREMENTS

Lean body mass by dual-energy X-ray absorptiometry, hand grip strength, a composite physical function score (chair stand and walking speed), 25(OH)D, parathyroid hormone (PTH), testosterone, age, race, body mass index, socioeconomic status, education, smoking, arthritis, self-reported health, calcium intake, physical activity.

RESULTS

The distributions of serum 25(OH)D quartiles differed by race/ethnicity, education and smoking status. After adjustment for multiple lifestyle factors, serum 25(OH)D was not related to lean body mass, grip strength or the composite physical function score (all P>0.20). There was no variation in the associations between 25(OH)D level and outcomes by race/ethnicity. The relationship between PTH and the outcomes revealed similar results.

CONCLUSION

In this population-based sample of adult men with a broad age range, there was no association between serum 25(OH)D concentration and lean body mass, muscle strength and physical function after controlling for multiple lifestyle factors.

Impact of supplementation with bicarbonate on lower-extremity muscle performance in older men and women

This study describes the impact of bicarbonate treatment for 3 months on net acid excretion (NAE), nitrogen excretion, and muscle performance in older men and women. Bicarbonate reduced NAE, and the decrement was associated with a decrease in nitrogen excretion. Treatment also improved muscle power and endurance in the women.

INTRODUCTION

Bicarbonate enhances muscle performance during strenuous exercise, but its effect on performance during normal activity in older subjects is unknown.

METHODS

In this trial, healthy subjects age 50 and older were randomized to 67.5 mmol of bicarbonate or to no bicarbonate daily for 3 months. Changes in lower-extremity muscle power, endurance, urinary nitrogen, and NAE were compared across treatment groups in the 162 participants included in the analyses.

RESULTS

In the men and the women, bicarbonate was well tolerated, and as expected, it significantly decreased NAE. The change in NAE correlated with change in nitrogen excretion in women (r = 0.32, P = 0.002) with a similar trend in men (r = 0.23, P = 0.052). In the women, bicarbonate increased double leg press power at 70% one repetition maximum by 13% (P = 0.003) compared with no bicarbonate and improved other performance measures. Treatment with bicarbonate had no significant effect on muscle performance in the men.

CONCLUSIONS

Ingestion of bicarbonate decreased nitrogen excretion and improved muscle performance in healthy postmenopausal women. The bicarbonate-induced decline in NAE was associated with reduced nitrogen excretion in both men and women. These findings suggest that bicarbonate merits further evaluation as a safe, low-cost intervention that may attenuate age-related loss of muscle performance and mass in the elderly.

Multi-step immunofluorescent analysis of vitamin D receptor loci and myosin heavy chain isoforms in human skeletal muscle

Vitamin D receptors have been shown to be present in human skeletal muscle using different techniques. We developed a multi-staining immunofluorescent method to detect vitamin D receptor expression and co-localize it with myosin heavy chain isoform expression in skeletal muscle biopsies in older female subjects. Serial sections were cut from frozen samples obtained by needle biopsy of the vastus lateralis. Samples were probed with a primary vitamin D receptor monoclonal antibody and then re-probed with a type IIa myosin heavy chain isoform-specific antibody. Independent unfixed sections followed a similar protocol and were probed with type IIx and type I myosin heavy chain isoform-specific antibodies. Immunohistochemistry and fluorescent microscopy co-localized vitamin D receptor loci and myosin heavy chain isoforms in whole skeletal muscle sections. We quantified intranuclear vitamin D receptor staining patterns and number of individual muscle fiber subtypes within a muscle section. Immunohistochemical staining of the vitamin D receptor was confirmed by Western blot using the same monoclonal antibody. This multi-staining immunofluorescent technique allows for measurement of intranuclear vitamin D receptor expression in the context of the specific muscle fiber type profile in a single section. This method can thus be a useful approach to study potential relationships between muscle fiber subtypes and vitamin D receptor expression.

Evaluation of an inexpensive calcium absorption index in healthy older men and women

OBJECTIVE

Calcium absorption is an important determinant of calcium retention and bone metabolism. However, most methods of measuring calcium absorption, including the well-established dual stable isotope method, are costly and cumbersome to implement. We evaluated whether an oral calcium tolerance test (OCTT), which involves measuring calcium excretion in a fasting 2-h urine collection and two 2-h collections following an oral calcium dose, may be a useful index of calcium absorption in older adults consuming a fixed calcium intake of 30 mmol/day.

DESIGN

After a 10-day metabolic diet containing 30 mmol/day of calcium, subjects had calcium absorption measured using the dual stable isotope method and the OCTT.

PARTICIPANTS

Eleven healthy subjects aged 54-74 years.

MEASUREMENTS

Fractional calcium absorption (FCA), calcium excretion in a fasting 2-h urine collection and two 2-h collections in response to a 10-mmol calcium dose (total intake 30 mmol/day).

RESULTS

Calcium excretion from several combinations of the urine collections was examined in relation to FCA. The most predictive of FCA was calcium excretion 4 h following the calcium dose. This measure was significantly correlated with FCA (r = 0.735, P = 0.010), fitting 54% of the variability in FCA.

CONCLUSION

Urinary calcium excretion during the 4 h after a 10-mmol calcium dose is a useful index of calcium absorption among older adults consuming recommended calcium intakes. This test is inexpensive, easy to implement and potentially useful in large clinical studies.

Vitamin D and its role in skeletal muscle

PURPOSE OF REVIEW

Vitamin D is best known for its role in regulating calcium homeostasis and in strengthening bone. However, it has become increasingly clear that it also has important beneficial effects beyond the skeleton, including muscle. This review summarizes current knowledge about the role of vitamin D in skeletal muscle tissue and physical performance.

RECENT FINDINGS

Molecular mechanisms of vitamin D action in muscle tissue include genomic and nongenomic effects via a receptor present in muscle cells. Knockout mouse models of the vitamin D receptor provide insight into understanding the direct effects of vitamin D on muscle tissue. Vitamin D status is positively associated with physical performance and inversely associated with risk of falling. Vitamin D supplementation has been shown to improve tests of muscle performance, reduce falls, and possibly impact on muscle fiber composition and morphology in vitamin D deficient older adults.

SUMMARY

Further studies are needed to fully characterize the underlying mechanisms of vitamin D action in human muscle tissue, to understand how these actions translate into changes in muscle cell morphology and improvements in physical performance, and to define the 25-hydroxyvitamin D level at which to achieve these beneficial effects in muscle.

A simple single serum method to measure fractional calcium absorption using dual stable isotopes

The dual stable isotope method with a timed 24-h urine collection is the gold standard approach to measure fractional calcium absorption. However, the need to collect urine for 24 h makes this technique time-consuming and laborious. Our study sought to determine whether a dual isotope method using a single serum sample obtained 4 h after administration of the initial isotope provides a useful approach to measure fractional calcium absorption. Following a metabolic diet with a fixed calcium intake of 30 mmol/day for 10 days, nineteen healthy subjects age 54-74 were given a test meal with an oral isotope ((44)Ca) followed 2 h later by an intravenous isotope ((42)Ca). Once the oral isotope was administered, urine was collected for 24 h, and a serum sample was obtained after 4 h. The ratio of the oral to intravenous isotopes was measured in the urine and serum by mass spectroscopy. Fractional calcium absorption was 16.2 ± 7.7% by the 4-h single serum method versus 18.5 ± 7.5% by the 24-h urine method. There was a small mean difference between the urine and serum methods of 2.33% with a confidence interval -3.97 to 8.60%. The two methods showed a strong linear association (r = 0.912, p<0.001). Use of dual stable isotopes with a 4-h single serum method gives fractional calcium absorption values that are 12.5% lower than with the 24-h urine method; however, it rank orders subjects accurately thus making it a useful alternative method in clinical research applications.

Potassium bicarbonate attenuates the urinary nitrogen excretion that accompanies an increase in dietary protein and may promote calcium absorption

CONTEXT

Protein is an essential component of muscle and bone. However, the acidic byproducts of protein metabolism may have a negative impact on the musculoskeletal system, particularly in older individuals with declining renal function.

OBJECTIVE

We sought to determine whether adding an alkaline salt, potassium bicarbonate (KHCO3), allows protein to have a more favorable net impact on intermediary indices of muscle and bone conservation than it does in the usual acidic environment.

DESIGN

We conducted a 41-d randomized, placebo-controlled, double-blind study of KHCO3 or placebo with a 16-d phase-in and two successive 10-d metabolic diets containing low (0.5 g/kg) or high (1.5 g/kg) protein in random order with a 5-d washout between diets.

SETTING

The study was conducted in a metabolic research unit.

PARTICIPANTS

Nineteen healthy subjects ages 54-82 yr participated.

INTERVENTION

KHCO3 (up to 90 mmol/d) or placebo was administered for 41 d.

MAIN OUTCOME MEASURES

We measured 24-h urinary nitrogen excretion, IGF-I, 24-h urinary calcium excretion, and fractional calcium absorption.

RESULTS

KHCO3 reduced the rise in urinary nitrogen excretion that accompanied an increase in protein intake (P = 0.015) and was associated with higher IGF-I levels on the low-protein diet (P = 0.027) with a similar trend on the high-protein diet (P = 0.050). KHCO3 was also associated with higher fractional calcium absorption on the low-protein diet (P = 0.041) with a similar trend on the high-protein diet (P = 0.064).

CONCLUSIONS

In older adults, KHCO3 attenuates the protein-induced rise in urinary nitrogen excretion, and this may be mediated by IGF-I. KHCO3 may also promote calcium absorption independent of the dietary protein content.

Activation of the calcium sensing receptor stimulates gastrin and gastric acid secretion in healthy participants

In 17 adults on a fixed metabolic diet, an 11-day course of cinacalcet increased serum gastrin and basal gastric acid output, but not maximal gastric acid output, compared with a placebo. These findings indicate that the calcium sensor receptor plays a role in the regulation of gastric acid.

INTRODUCTION

Gastric acid secretion is a complex process regulated by neuronal and hormonal pathways. Ex vivo studies in human gastric tissues indicate that the calcium sensing receptor (CaR), expressed on the surface of G and parietal cells, may be involved in this regulation. We sought to determine whether cinacalcet, a CaR allosteric agonist, increases serum gastrin and gastric acid secretion.

METHODS

Seventeen healthy adults with normal gastric acid output were placed on an 18-day metabolic diet. On day 8 (baseline), participants were given cinacalcet (15 then 30 mg/day) or placebo for 11 days. Changes in gastric acid output, serum gastrin, and other measures were compared in the two groups.

RESULTS

Changes in serum gastrin and basal acid output (adjusted for baseline body weight) were significantly more positive in the cinacalcet group compared with placebo (P = 0.004 and P = 0.039 respectively). Change in maximal acid output was similar in the two groups (P = 0.995). As expected, cinacalcet produced significant decreases in serum PTH (P < 0.001) and ionized calcium levels (P = 0.032), and increases in serum phosphorus levels (P = 0.001) and urinary calcium (P = 0.023).

CONCLUSIONS

This study provides in vivo evidence that activation of the CaR increases serum gastrin levels and basal gastric acid secretion in healthy adults.

Vitamin D and skeletal muscle tissue and function

This review aims to summarize current knowledge on the role of vitamin D in skeletal muscle tissue and function. Vitamin D deficiency can cause a myopathy of varying severity. Clinical studies have indicated that vitamin D status is positively associated with muscle strength and physical performance and inversely associated with risk of falling. Vitamin D supplementation has shown to improve tests of muscle function, reduce falls, and possibly impact on muscle fiber composition and morphology in vitamin D deficient older adults. Molecular mechanisms of vitamin D action on muscle tissue include genomic and non-genomic effects via a receptor present in muscle cells. Genomic effects are initiated by binding of 1,25-dihydroxyvitamin D [1,25(OH)(2)D] to its nuclear receptor, which results in changes in gene transcription of mRNA and subsequent protein synthesis. Non-genomic effects of vitamin D are rapid and mediated through a cell surface receptor. Knockout mouse models of the vitamin D receptor provide insight into understanding the direct effects of vitamin D on muscle tissue. Recently, VDR polymorphisms have been described to affect muscle function. Parathyroid hormone which is strongly linked with vitamin D status also may play a role in muscle function; however, distinguishing its role from that of vitamin D has yet to be fully clarified. Despite the enormous advances in recent decades, further research is needed to fully characterize the exact underlying mechanisms of vitamin D action on muscle tissue and to understand how these cellular changes translate into clinical improvements in physical performance.

Alkaline diets favor lean tissue mass in older adults

BACKGROUND

Maintaining muscle mass while aging is important to prevent falls and fractures. Metabolic acidosis promotes muscle wasting, and the net acid load from diets that are rich in net acid-producing protein and cereal grains relative to their content of net alkali-producing fruit and vegetables may therefore contribute to a reduction in lean tissue mass in older adults.

OBJECTIVE

We aimed to determine whether there was an association of 24-h urinary potassium and an index of fruit and vegetable content of the diet with the percentage lean body mass (%LBM) or change in %LBM in older subjects.

DESIGN

Subjects were 384 men and women > or =65 y old who participated in a 3-y trial comparing calcium and vitamin D with placebo. Potassium was measured in 24-h urine collections at baseline. The %LBM, defined as total body nonfat, nonbone tissue weight/weight x 100, was measured by using dual-energy X-ray absorptiometry at baseline and at 3 y. Physical activity, height, and weight were assessed at baseline and at 3 y.

RESULTS

At baseline, the mean urinary potassium excretion was 67.0 +/- 21.1 mmol/d. Urinary potassium (mmol/d) was significantly positively associated with %LBM at baseline (beta = 0.033, P = 0.006; adjusted for sex, weight, and nitrogen excretion) but not with 3-y change in %LBM. Over the 3-y study, %LBM increased by 2.6 +/- 3.6%.

CONCLUSION

Higher intake of foods rich in potassium, such as fruit and vegetables, may favor the preservation of muscle mass in older men and women.

Meta-analysis: efficacy and safety of inhaled insulin therapy in adults with diabetes mellitus

BACKGROUND

Injection insulin therapy is not readily accepted by patients and many health care providers; therefore, less invasive options for insulin therapy are desirable.

PURPOSE

To examine the efficacy, safety, and patient acceptability of inhaled insulin therapy in nonpregnant adults with diabetes mellitus.

DATA SOURCES

English-language studies in MEDLINE, the Cochrane Clinical Trials Register (through June 2006), and U.S. Food and Drug Administration review documents of the first formulation of inhaled insulin approved for clinical use.

STUDY SELECTION

Randomized, controlled trials of at least 12 weeks' duration that compared inhaled insulin with another active therapy and reported hemoglobin A1c levels in adults with type 1 or type 2 diabetes mellitus.

DATA EXTRACTION

Two reviewers independently assessed trials for inclusion and extracted data. Differences were resolved by consensus.

DATA SYNTHESIS

Sixteen open-label trials met the inclusion criteria (4023 patients; age range, 18 to 80 years). Among patients with type 1 or type 2 diabetes, there was a small decrease in hemoglobin A1c level from baseline that favored subcutaneous insulin over inhaled insulin (weighted mean difference, 0.08% [95% CI, 0.03% to 0.14%]), although there was no difference in the proportion of participants achieving hemoglobin A1c levels less than 7%. Inhaled insulin lowered hemoglobin A1c levels more (weighted mean difference favoring inhaled insulin, -1.45% [CI, -1.80% to - 1.10%]) compared with fixed doses of oral agents but much less when compared with oral agents titrated to glycemic efficacy (weighted mean difference favoring inhaled insulin, -0.20% [CI, -0.34% to - 0.07%]). Severe hypoglycemia was more likely to occur with inhaled insulin than with oral agents (risk ratio, 3.1 [CI, 1.0 to 9.1]), but there was no increased risk compared with subcutaneous insulin. There was an increased incidence of mild to moderate nonprogressive dry cough in patients treated with inhaled insulin (risk ratio, 3.5 [CI, 2.2 to 5.6]) and a mild decrease in certain pulmonary function testing variables, which did not progress over 2 years. Patients preferred inhaled insulin over subcutaneous insulin.

LIMITATIONS

All trials were open label, which may introduce bias. Most of the trials were of 24 weeks' duration or less, limiting assessment of long-term safety.

CONCLUSIONS

Inhaled insulin offers an alternative noninvasive option for premeal insulin administration, with glycemic efficacy slightly less than subcutaneous regular insulin and increased patient acceptability. Until long-term safety data are available, inhaled insulin should be reserved for nonpregnant adults with diabetes who are opposed to injections and who would otherwise delay appropriate and timely therapy with insulin.

[Peridural analgesic therapy in orthopedic surgery: comparison of ropivacaine and bupivacaine]

The aim of our study was to compare the efficiency of ropivacaine and bupivacaine, in epidural administration, in postoperative analgesia. 20 patients, undergone knee surgery, in epidural anaesthesia (bupivacaine 0.5%-2 mg/Kg-1 administered in level L3L4), was divided into 2 groups (10 each one) and the local anaesthetics in study was administered by epidural catheter with an elastomeric pump: A (ropivacaine 0.15%) and B (bupivacaine 0.15%). The results demonstrate that ropivacaine is better than bupivacaine to keep a check on analgesia in postoperative pain.

[Use of mivacurium in orthopedic surgery: comparison of 2 different-dose inductions]

The aim of our study was to evaluate the efficiency and safety of mivacurium, comparing two dose-induction in patients undergone a minor orthopaedic surgery. 30 patients were divided into two groups and mivacurium were administered at the dose of 0.15 mg Kg-1 and 0.20 mg Kg-1 respectively. The results confirmed its efficiency in short surgery. Mioresolution was excellent only in the second group (0.20 mg Kg-1) despite an histamine-related blood pressure reduction.

[Use of ropivacaine in axillary brachial plexus block]

The aim of the study was to evaluate the efficiency and safety of ropivacaine, in comparison with bupivacaine, in axillary brachial plexus block. 24 patients, undergoing upper limb surgery, was divided into 2 homogeneous groups and the local anaesthetics was administered: A (ropivacaine 0.75%, 25 ml; total dose 187.5 mg) and B (bupivacaine 0.5%, 25 ml; total dose 125 mg). The axillary plexus block was executed with the help of an electrostimulator. The results show that using ropivacaine the onset-time is lower and the duration of sensory and motor block is higher than using bupivacaine. In conclusion we can affirm that ropivacaine is a new step in local anaesthetic field.