PTH And Calcium Responses to Exercise in Older Adults Experiment 2 (PACE Sr. 2)

Declines in serum calcium during exercise may cause increases in markers of bone resorption. This study will determine if preventing the decline serum ionized calcium experienced at the onset of exercise through the use of a "calcium clamp" also prevents increases in blood biomarkers associated with bone resorption.

Study Overview

• Status: Completed
• Conditions: Osteoporosis
• Intervention / Treatment: Drug: Calcium Chloride/Calcium Gluconate; Drug: Half-Normal Saline

Detailed Description

Participants will undergo two identical walking exercise sessions on a treadmill. One session will occur until continuous calcium infusion and the other will be under continuous saline infusion. C-telopeptide, parathyroid hormone, total calcium, and serum ionized calcium will be monitored to distinguish differences in bone activity under the two conditions.

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Colorado
    • Aurora, Colorado, United States, 80045
      • University of Colorado Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 60 years to 80 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy adults aged 60-80 y
• Currently taking a bisphosphonate medication

Exclusion Criteria:

• Use of medications (other than bisphosphonates) in the past 6 months known to affect bone metabolism (e.g., thiazide diuretics, oral glucocorticoids)
• Bone Mineral Density (BMD) t score < -3.0 at the total hip or lumbar spine
• Known disease or condition associated with intestinal malabsorption
• Moderate or severe renal impairment defined as an estimated glomerular filtration rate of <60 mL/min/1.73m2 based on the Modified Diet in Renal Disease (MDRD) equation
• Chronic hepatobiliary disease, defined as liver function tests (AST, ALT) >1.5 times the upper limit of normal; if such values are obtained on initial screening and thought to be transient in nature, repeated testing will be allowed
• Thyroid dysfunction, defined as an ultrasensitive TSH <0.5 or >5.0 mU/L; volunteers with abnormal TSH values will be re-considered for participation in the study after follow-up evaluation by the PCP with initiation or adjustment of thyroid hormone replacement
• Serum calcium <8.5 or >10.3 mg/dL Serum 25(OH)D <20 ng/mL; volunteers with abnormal serum 25(OH)D values may be re-considered for participation in the study if serum 25(OH)D is >20 ng/mL after vitamin D supplementation
• Uncontrolled hypertension defined as resting systolic BP >150 mmHg or diastolic BP>90 mmHg; participants who do not meet these criteria at first screening will be re-evaluated, including after follow-up evaluation by the PCP with initiation or adjustment of anti-hypertensive medications
• History of type 1 or type 2 diabetes
• Cardiovascular disease; subjective or objective indicators of ischemic heart disease (e.g., angina, ST segment depression) or serious arrhythmias at rest or during the graded exercise test (GXT) without follow-up evaluation will be cause for exclusion; follow-up evaluation must include diagnostic testing (e.g., stress echocardiogram or thallium stress test) with interpretation by a cardiologist
• Diagnosis or history of asthma

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Calcium Infusion followed by Saline Infusion; All participants will have a continuous calcium infusion during exercise at their first collection visit. The second collection visit will always be a volume-matched half-normal saline infusion.

Drug: Calcium Chloride/Calcium Gluconate; Calcium (as either calcium chloride or calcium gluconate in half normal saline) will be delivered via IV during exercise to keep serum ionized calcium levels above baseline. The clamp is modeled after the hyperglycemic glucose clamp.; Drug: Half-Normal Saline; This is the placebo comparative infusion. Half-normal saline will be infused at the second collection visit following the identical infusion schedule determined during the calcium infusion visit.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Parathyroid Hormone (PTH)	Change in PTH will be measured from baseline to end of exercise	baseline, 60 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in C-telopeptide (CTX)	Change in CTX will be measured from baseline to the end of 60 minutes of exercise	baseline, 60 minutes
Change in Ionized Calcium	Change in ionized calcium will be measured from baseline to the end of 60 minutes of exercise	baseline, 60 minutes

Collaborators and Investigators

• Sponsor: University of Colorado, Denver
• Collaborators: National Center for Advancing Translational Sciences (NCATS)
• Investigators: Principal Investigator: Sarah J Wherry, PhD, University of Colorado, Denver

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2015
• Primary Completion (Actual): July 31, 2024
• Study Completion (Actual): July 31, 2025

Study Registration Dates

• First Submitted: October 16, 2015
• First Submitted That Met QC Criteria: October 16, 2015
• First Posted (Estimated): October 20, 2015

Study Record Updates

• Last Update Posted (Actual): August 13, 2025
• Last Update Submitted That Met QC Criteria: August 11, 2025
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Metabolic Diseases; Bone Diseases, Metabolic; Osteoporosis; Calcium-Regulating Hormones and Agents; Physiological Effects of Drugs; Calcium
• Other Study ID Numbers: 15-0878; UM1TR004399 (U.S. NIH Grant/Contract)