Metabolic Phenotyping in Humans
Metabolic Phenotyping in Humans
Type 2 diabetes (T2D) is a global burden disease affecting almost 200 million people and is
 expected to nearly double by 2030 (1). It is imperative that this disease is kept under
 control, and that we begin to reverse the direction of its incidence. We propose to start by
 identifying the physiological and molecular aspects of the problem in all spectrums of the
 disease (ie from insulin sensitive athletes to sedentary lean and obese individuals and
 further to overt type 2 diabetics), and focus our efforts on examining the differences and
 identifying the stages of progression for possible targets of future intervention. The
 proposed study "Metabolic Phenotyping" is novel in its target populations and innovative in
 its use of state-of-the-art techniques. We hypothesize that the in vivo differences in
 metabolic flexibility and mitochondrial function between endurance athletes and type 2
 diabetics and their lean and obese controls are retained in vitro and will offer a new model
 in which to study the underlying mechanisms of the progression of T2D.
The aim of the present research proposal is to metabolically phenotype endurance trained
 athletes, lean and obese sedentary and type 2 diabetic individuals with the following
 objectives:

 1. assess metabolic flexibility as measured by a euglycemic-hyperinsulinemic clamp

 2. measure in vivo mitochondrial function by MRS of phosphocreatine (PCr) recovery

 3. establish primary myoblast cell lines to correlate with the above in vivo measurements,
 as well as further explore dietary, pharmacological and genetic manipulations in vitro

 4. quantify intramyocellular lipid (IMCL) and acetylcarnitine in vivo by MRS

 Study population:

 A total of 132 male participants (18-70 years) will participate in this study. The first
 group of 33 participants will be lean endurance-trained athletes, the second group will be
 lean sedentary control participants, the third group will be sedentary type 2 diabetic
 participants, and the last group of 33 participants will be obese, non-diabetic sedentary
 control participants. It is preferred to use male participants in order to minimize variation
 in the measurements by avoiding confounding factors such as hormones.

 Main study parameters/endpoints: The main study parameters are differences in metabolic
 flexibility as measured by euglycemic-hyperinsulinemic clamp, PCr recovery, IMCL and
 acetylcarnitines as measured by MRS and establishment of primary myoblast cell lines for
 future use.
General Inclusion criteria:

 -  Male sex

 -  Generally healthy with specifically no known cardiovascular disease or gastric ulcers,
 which can affect the study parameters

 -  Stable dietary habits (no weight loss/gain > 3 kg in the last 6 months)

 Group 1, type 2 diabetes participants:

 -  Ages 40-70 years

 -  BMI > 30 kg/m2

 -  Non-insulin dependent type 2 diabetes

 -  Must be on sulphonylurea (SU)-derivate or metformin therapy for at least six months
 with a constant dose for at least two months, or on dietary treatment for at least six
 months

 -  Well-controlled diabetes: HbA1c < 8%

 -  No diabetes related co-morbidities like cardiovascular diseases, diabetic foot,
 polyneuropathy, retinopathy

 Group 2, obese healthy control participants:

 -  Ages 40-70 years

 -  BMI > 30 kg/m2

 -  A plasma glucose level lower than 6.1 mmol/L

 -  No family history of diabetes

 -  No medication use

 -  Sedentary lifestyle; No participation in any physical activity for at least 2 years

 Group 3, endurance trained athletes:

 -  Ages 18-35 years

 -  BMI < 25 kg/m2

 -  No family history of diabetes

 -  No medication use

 -  VO2max > 55ml/kg/min

 -  Active in competitive endurance-exercise activities, 3 times a week for at least 2
 years

 -  Stable level of training for at least 6 months

 Group 4, lean healthy sedentary control participants:

 -  Ages 18-35 years

 -  BMI < 25 kg/m2

 -  No family history of diabetes

 -  No medication use

 -  VO2max < 55ml/kg/min

 -  Plasma glucose < 6.1 mmol/L

 -  Sedentary lifestyle; No participation in physical activity for more than 1 hour per
 week for at least 2 years

 General Exclusion criteria:

 -  Regular smokers

 -  Participation in other studies

 -  Female sex

 -  Insulin dependent diabetic individuals

 -  Participants with diabetes related diseases (diabetic foot, diabetic polyneuropathy,
 diabetic retinopathy etc.)

 -  Use of Thiazolidines (glitazone/rosiglitazone/pioglitazone/troglitazone)

 -  Use of anti-coagulants (not thrombocyte-aggregation inhibitors)

 -  Aberrant ECG (with signs of ischemia or cardiac failure or arrythmias)

 -  Weight gain/loss > 3 kg in the last 6 months

 -  HbA1c < 7.8 in type 2 diabetic individuals

 -  Contraindications for MRS scans:

 -  Electronic implants such as pacemakers or neurostimulator

 -  Iron-containing foreign bodies in eyes or brain

 -  Some hearing aids and artificial (heart) valves which are contraindicated for MRS

 -  Claustrophobia

 -  Participants, who do not want to be informed about unexpected medical findings, or do
 not wish that their physician be informed, cannot participate in the study.