HORMONE AND METABOLITE CORE

INTRODUCTION

This Laboratory has been in operation since the Core Center was first funded in 1980. It has been used very heavily because it has been extraordinarily helpful for investigators not to have to set up methods for analyses that are more efficiently done here. The use of this laboratory by scientific associates continues to be high and allows for greater productivity at lesser cost for Investigators.

PURPOSE AND SERVICES OF THE HORMONE/METABOLITE SUB-CORE

The purpose of the Hormone/Metabolite Core Laboratory is to make available to NYORC investigators a variety of analytical techniques that are of interest in the study of obesity, eating disorders, and related problems. The services provided are best based in a Core Laboratory because they require special instrumentation and methodology which would be difficult or impracticably expensive to establish in the laboratories of the individual investigators of the NYORC.

In investigations of ingestive behavior, efficiency of energy use, hormonal action, dietary intervention, molecular genetics, or drug effects, it is essential to be able to monitor suitable markers of metabolic status. It is often helpful to measure changing concentrations of hormones such as insulin, glucagon, or catecholamines and such substrates as glucose, free fatty acids, glycerol, ketones, and lipids. It may be useful to correlate these patterns with other phenomena, subjective or objective, relevant to the hypotheses being tested.

In subjects who are losing or gaining fat on different regimens, it is important to have information about such parameters as glucose tolerance, insulin sensitivity, hepatic glucose output, plasma lipids and lipoproteins, amino acids, and ketones in the blood and urine, etc. There is a clear rationale for obtaining information about hormone?fuel concentrations in the course of studies concerned with the categorization of obesity, energy balance, ingestive behavior, and related problems.

The purpose of the Hormone/Metabolite Core is:

1. to provide NYORC investigators with an array of analytical techniques that are important in the study of obesity, eating disorders, and related problems. The bringing together of these services in one laboratory allows for efficiency, high quality, and low cost.
2. to provide advice on the advantages, limitations, and problems with the various analytical methods, and to give consultative help to Users on the technology and methodology, on design of experiments, and on interpretation of results obtained.
3. to provide training and education to Users so that they will become knowledgeable in the technology of the methodology and, if necessary, be able to transplant analytical methods to their own laboratories.
4. to respond to investigators' needs by undertaking on new methods that the expertise of the Core staff can develop and that can help in their research endeavors, thereby enhancing their productivity.
5. to increase the collaborative interests of different Users by informing them of others' work and bringing them together in new research endeavors.

OVERVIEW OF TECHNIQUES AND SERVICES OFFERED

The Core Laboratory provides the following services to cooperating investigators (Users), namely, measurement of:

• Hormones (in biological fluids, notably plasma, serum, or urine, depending on the particular hormone and the particular study).
  a. insulin
  b. free insulin
  c. C_peptide
  d. free C_peptide
  e. growth hormone
  f. glucagon
  g. gastrin
  h. triiodothyronine
  i. thyroxine (T4)
  j. reverse T3
  k. thyroid stimulating hormone (TSH)
  l. aldosterone
  m. renin
  n. cortisol
  o. testosterone
  p. estradiol
  q. leptin
  r. follicle stimulating hormone
  s. luteinizing hormone
  t. DHEA
  
  
• Metabolites (in biological fluids, notably plasma, serum, or urine, depending on the particular metabolite and the particular need of the investigator).
  a. glucose
  b. free fatty acids (FFA)
  c. glycerol
  d. acetoacetate
  e. beta_hydroxybutyrate
  f. lactate
  g. pyruvate
  h. hemoglobin Alc
  i. Alanine
  j. glycogen in tissue (liver or muscle)
  k. creatinine
  l. 3-methyl histidine
  m. hs-CRP
  
  
• Lipids and lipoproteins.
  a. total cholesterol
  b. phospholipid
  c. triglyceride
  d. lipoprotein spectrum by preparatory ultracentrifugation
  e. HDL cholesterol
  f. LDL cholesterol
  g. apolipoprotein E
  h. other selected apolipoproteins
  
  
• Tracer radioisotope techniques for metabolic studies. Isotope measurements for metabolic studies can be set up for cooperating investigators as needed. Examples in the previous grant period have been:
  a. human hepatic glucose output by tritiated glucose (65)
  b. glucose transport utilizing 14C-glucose, in vitro.
  

Other special procedures for which the Core Director and Associate Director are available for consultation

• glucose-insulin clamp methodology including pancreatic clamps, in vivo
• minimal model insulin sensitivity methodology
• preparation of infusates for hormones or tracer isotope infusions, in vivo
• adipose tissue studies including adipocytes isolation, metabolite fluxes and insulin action in vitro

QUALITY CONTROL

A great deal of effort is made in the Hormone and Metabolite Core to ensure that the determinations that are done are accurate and reproducible. Calibration of appropriate instruments is carried out at regular intervals and generally before any run of samples. In the radioimmunoassays, high and low controls as well as standards are routinely run. Standard curves are routinely measured with every assay run, and standard curves are compared from assay to assay for gross changes or deviations from normal. Also, duplicates and non-specific binding tubes are always run on all samples. If duplicates are more than a certain percentage apart (depending on the hormone assay), the samples are re-run. For lipid and lipoprotein measurements, standards and calibrators are purchased from a commercial company. For a number of samples, periodic measurements of unknown samples provided by the College of American Pathologists and the Joint Commission for Accreditation of Hospital Pathologists are used. In summary, quality control is a crucial issue for the reliability of the results given to investigators, and thus is a high priority of the Core Laboratory Director.

CONTACT INFORMATION

F. X. Pi-Sunyer, MD, MPh
New York Obesity Research Center
St. Luke's/Roosevelt Hospital Center
1111 Amsterdam Avenue - Rm 1020
New York, NY 10025

Phone - (212) 523-4161
Fax - (212) 523-4830
E-mail - fxp1@columbia.edu