Effect of Dietary Conjugated Linoleic Acid (CLA) on Parathyroid Hormone in Men
Condition: Healthy
Study type: Interventional
Phase: Phase 1

Summary: 
      The parathyroid gland and its hormone have a major impact on the endocrine control of bone
      metabolism and mineralization and parathyroid hormone (PTH) has been identified in some
      epidemiological reports to relate adversely to mortality. Previously, the applicant has
      demonstrated in two models that dietary cis-9, trans-11 conjugated linoleic acid (CLA)
      reduces PTH by over 30% in as little as 4 weeks in male rats without adversely affecting bone
      density. Both bioactive PTH and intact PTH assays have been used and both are reduced by CLA.
      In one rat model, rats had normal PTH and a sub-group had high PTH due to chronic renal
      disease. In the second study, the rats were healthy young males and females. Regardless of
      the model and health state, PTH was reduced 30 to 40% by CLA. Of interest, other isoforms of
      CLA such as trans-10, cis-12 CLA do not alone result in reduced PTH. The selected CLA isomer
      proven to reduce PTH, cis-9, trans 11 CLA, is common to food products such as milk fat and
      beef and is thus more physiologically relevant to the human diet. The global objective of
      this study is to, for the first time; assess the effects of CLA on PTH in humans,
      specifically men.

      Healthy men 19-53 years of age are selected since bone mass will have reached a peak by this
      age. Beginning with healthy relatively young men is important versus aging or ill individuals
      since the effect of CLA on PTH has not been examined and aging and illness might confound the
      results.

      Subjects will be recruited using posters and local newspaper advertisements from the general
      population. Men (n=30/group) with healthy weights will be randomized to receive 0, 1.5 or 3 g
      CLA/d for a period of 4 months. At baseline, body weight will be assessed along with whole
      body bone, lean and fat mass using dual energy x-ray absorptiometry (DXA). Regional bone mass
      (lumbar spine, total hip, femoral neck) will also be examined using DXA. A blood sample will
      be taken in the fasted state between 9:00 and 10:00 to examine PTH, ionized Ca, and
      biomarkers of bone metabolism. After each 1 month on the study, the measurements will be
      repeated until end of study.

      Dietary intake will be monitored along with a survey for possible mild side-effects such as
      gastrointestinal discomfort. Data will be examined using a mixed model for random (age,
      weight, vitamin D status) and fixed effects (diet, time) with post-hoc comparisons using
      Bonferroni correction.
    

Detailed description: 
      EXPERIMENTAL DETAILS The global objective of this study is to, for the first time; assess the
      effects of CLA on PTH in humans, specifically men.

      Primary Objectives and Hypotheses, in healthy men 40 years of age are to determine if:

        1. Cis-9, trans-11 CLA reduces PTH;

           a. it is hypothesized that CLA will reduce PTH by 30%.

        2. The effect is transient; b. it is hypothesized that PTH will fall within 4 weeks of
           treatment and remain stable thereafter over the 4 months of study.

        3. Short-term changes in bone metabolism accompany reductions in PTH following dietary
           intake of CLA; c. it is hypothesized that bone resorption will be reduced as indicated
           by resorption markers and the ratio of osteoprotegerin to RANKL.

      Secondary Objective and Hypothesis is to determine if:

      1) Dietary CLA and plasma CLA at baseline are related to bone mass and metabolism;

      a. it is hypothesized that higher dietary intakes of CLA and higher plasma CLA will be
      associated with higher bone mineral density (BMD) and lower bone resorption.

      Experimental Design and Methods Population: Healthy men 19 to 53 years of age are selected
      since bone mass will have reached a peak by this age. Beginning with healthy relatively young
      men parallels the observations from the animal studies in male rats that were at an age when
      peak bone mass was already achieved (5 mo). These participants will be recruited from the
      Greater Montreal area; primarily the Macdonald Campus of McGill University and also through
      announcements made in the local newspapers (West Island Gazette). All study visits will take
      place at the Mary Emily Clinical Nutrition Research Unit, School of Dietetics and Nutrition
      (Directed by Dr. Weiler).

      The sample size will be 90 healthy men (n=30/group) based on the following inclusion
      criteria:

      healthy body weight based on body mass index (18.5 - 25 kg/m2 as per Health Canada (50)), no
      chronic diseases, normal bone mass for age (ie Z-score better than -1 where reference data
      available), and vitamin D status within optimal range based on serum 25(OH)D (between 50 and
      80 nmol/L of serum 25(OH)D with a median threshold of 75 nmol/L as set by international
      experts (24)).

      Vitamin D status will be an inclusion criterion since seasonal changes in vitamin D status
      will alter PTH. Participants who meet the entry criteria upon screening must also continue to
      meet the entry criteria 1 month later when the supplementation begins (see figure 3 for flow
      diagram of study time-line for year 1). This is important as related to vitamin D status and
      possible interactions with PTH. The error of the vitamin D assay is <10%. Thus measurements
      at baseline within 10% of the screening value will enable continuance in the study. To ensure
      that the median threshold is maintained, screening will be set at 75 nmol/L of 25(OH)D and
      values >10 nmol/L will be accepted at inception. This will accommodate the range set for
      optimal vitamin D status and is thus 65 nmol/L and up in the present study.

      Protocol: In May and June of 2008 potential participants will be initially screened by
      telephone for health status, self-reported body weight and height and age. Upon meeting these
      criteria they will be asked to fast beginning the evening prior to the screening visit (12 h)
      that will include measurement of body weight, height and bone mass using dual-energy x-ray
      absorptiometry (DXA) to provide whole body and regional bone mass (lumbar spine, total hip,
      femoral neck) and a general health assessment by the study physicians. At this visit a 5 ml
      blood sample will be taken between 9 and 10 am to screen for 25(OH)D concentration. It is
      anticipated that in May-June the 25(OH)D will be within the targeted range in 50-75% of
      people screened based on the data of Looker et al for US men in northern latitudes in summer
      where mean values were 79 nmol/L in the northern attitude group of men 40 to 49 years of age
      (51). Those meeting criteria will be invited to participate in the trial for which men will
      be randomized to receive 0, 1.5 or 3 g CLA/d for a period of 4 months beginning in ~June of
      each year; half of the sample will be recruited each year to enable the monthly assessments
      accompanied by rapid measurement of CLA. Dietary assessment using a 24-hour food recall will
      establish typical intakes of CLA prior to baseline sampling by mailing the record a week in
      advance, followed by supplementation. At baseline, body weight and height will be measured
      along with DXA assessment of whole body and regional bone mass (lumbar spine, forearm, total
      hip, femoral neck). A food frequency questionnaire will be given to assess the relationship
      between CLA in the diet, CLA status and bone descriptively. A blood sample will be taken in
      the fasted state between 9:00 and 10:00 to examine PTH, ionized Ca, and markers of bone
      metabolism including osteocalcin (formation), osteoprotegerin, RANKL and N-telopeptide
      (resorption) and CLA in plasma and red cell membranes. This sampling time will accommodate
      the nadir in PTH as well as permit assessment of biomarkers of bone metabolism at a
      standardized am time. The measurements (except for the DXA) will be repeated monthly until
      end of study. Dietary intake will be monitored each month using a 24-hour food recall prior
      to each visit to enable clarifications in person. A survey for mild side-effects such as
      gastrointestinal discomfort will be conducted at each visit along with collection of all
      supplements not taken to estimate compliance. Since participants will be fasting for each
      visit, a small snack will be provided as tetra pack milk and a bagel after the measurements
      (under general supplies in budget). Participants will be asked to not exercise prior to the
      visit since moderately intense activity can elevate PTH (52).

      Details of Methodology Dietary Supplementation Approach: All supplements and placebo will be
      double-blinded by use of letter coding. Only the safety officer will know the treatment
      groups. Each participant will take the required number of placebo and/or CLA capsules with
      each lunch and dinner meal and be provided enough for one month at a time. At each visit all
      unused capsules will be recovered for compliance assessment and a new supply provided for the
      next month of study. Participants will be asked to maintain their current diet to prevent
      changes in body weight and body composition and also will be asked to keep their activity as
      constant as possible over the duration of study, also to keep body weight and composition
      constant as well as maintain weight bearing activities on bone. Diet will not be modified in
      this study, but rather monitored. At the screening assessment, a registered dietitian (3 RDs
      in Dr. Weiler's training program are available to provide this assessment) will provide all
      participants an assessment of current and usual intake against recommendations and then guide
      them on how to keep the diet both within recommendations and usual intakes. Participants will
      be instructed on what amounts of and types of snack foods will be permitted the evening prior
      to fasting. Of note, calcium intake in Montreal men is typically close to recommendations
      with ~80% achieving calcium intake at the recommended level (53, 54).

      The supplements will be Clarinol A95 (Lipid Nutrition) that is in free fatty acid form with
      80% of the CLA in the cis-9, trans-11 form and 20% in the trans-10, cis-12 isoform; this is
      the purest CLA available. Using supplements for this study is rationalized in order to follow
      the approach from the basic studies rather than food products enriched with CLA; ie, use
      diets with the supplemental CLA as used in the rodent study. Each supplement will be designed
      to provide half of the CLA dosage per meal. In this manner the 1.5 group will have capsules
      containing 0.75 g of CLA with the remaining weight comprised of placebo olive oil. For the 3
      g group, the CLA capsules will contain 1.5 g CLA. The placebo capsules will be olive oil.
      Each person will be asked to take one half-dose at lunch and one half-dose at dinner.

      Dietary and Supplement Intake: will be assessed at each visit using a 24-hour food recall.
      The data will be used to describe the intakes of the population with respect to total energy,
      macronutrients (protein, fat, carbohydrate) and micronutrients (Ca, P, Zn, Mg, vitamin D)
      that relate to bone and PTH metabolism. The food intake for the day prior to blood sampling
      is also important to establish the possible effects of an evening meal or snack prior to
      fasting for the am blood sampling. For example if the snack was high in calcium or if the
      participant did not eat the usual intake etc. values for PTH could be falsely low. The
      three-day record is selected to better assess intakes and is validated against plasma samples
      measured for CLA (5, 56). The dietary intake will have less of an impact on the plasma CLA
      after inception but the dietary intake of CLA is a necessary assessment to demonstrate
      sources of dietary CLA and to quantify total dietary CLA and enhance understanding of the
      plasma CLA values.

      Sample Procurement: Blood will be collected at all visits between 9:00 and 10:00 to control
      for diurnal variation permitting 3 to 4 participants to be seen in our Unit daily.

      Adverse Effects and Safety Monitoring: At each visit, participants will be asked using a
      check-box questionnaire if they experienced any illness or been treated for acute illnesses.
      Frequency of headaches, dizziness, constipation, cramping, nausea, vomiting, diarrhoea or
      abdominal pain will be documented. Any abnormal value will initiate a second sampling. Upon
      confirmation of abnormal values, the participant will be asked to stop taking the CLA
      supplement and have a subsequent blood sample taken at a follow-up visit to evaluate return
      of ionized Ca and PTH to expected values and they will fall into the intent-to-treat
      statistical analysis arm of the study. Blood pressure will be measured using standard radial
      cuff and sphygmomanometer and in supine position immediately following the DXA as part of the
      general health assessment.
    

Intervention name(s): Clarinol CLA
Intervention type(s): Dietary Supplement
Intervention description(s): 0, 1.5 or 3.0 g/d dietary conjugated linoleic acids glycerides for 4 months, capsule form
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: CLA; PTH; nutritional supplement