Fat and Glucose Metabolism in Fed and Fasted State in Patients With Low Skeletal Muscle Mass
Condition: Spinal Muscular Atrophy; Merosin Deficient Congenital Muscular Dystrophy
MeSH terms: Muscular Dystrophies; Muscular Atrophy; Muscular Atrophy, Spinal
Study type: Interventional

Summary: 
      In a study from 2003 the investigators showed that adult patients with very low skeletal
      muscle mass (spinal muscular atrophy (SMA) type II, Duchenne muscular dystrophy, congenital
      muscular dystrophy) are prone to develop hypoglycemia during prolonged fasting. Since then
      case reports have described the same phenomenon with hypoglycemia and metabolic crises in
      children with low skeletal muscle mass provoked by infection, fasting and surgery.
      Pathophysiological mechanisms of metabolism have never been investigated in adults or
      children with SMA II. Thus the investigators studied fat and glucose metabolism during
      prolonged fasting in patients with SMA II and LAMA 2 and compared results to those found in
      healthy controls.
    

Detailed description: 
      Design. This is a prospective case-control study investigating fat and glucose metabolism in
      patients with low muscle mass during prolonged fasting, comparing results to those found in
      healthy controls.

      Setting. All children were admitted to the Department of Pediatrics and Adolescents medicine,
      Rigshospitalet, and all adult subjects were admitted to the Department of Neurology,
      Rigshospitalet at 4 pm for a 24-hour fasting period.

      Protocol. The protocol consisted of two visits. A pre-experimental visit and a study visit.

      Pre-experimental visit. Total muscle mass presented as lean body mass (LBM) was measured by
      DEXA scan. Furthermore, pre-experimental preparations included that all subjects were
      instructed to follow national nutritional recommendations with a healthy diet consisting of
      less than 30% fat, low fat protein, long chain carbohydrates and minimize sugar intake three
      days before the study.

      Study visit. Patients were admitted to the hospital at 16:00 hours for IV catheter placement
      and a standardized evening meal at 17:00. Two venous catheters were inserted, one in the
      cubital vein (for stable-isotope infusion) and one in the distal cephalic vein (for blood
      sampling). A heating pad, covering the hand and distal forearm, ensured shunting of arterial
      blood to the veins in order to obtain arterialized blood. A primed, constant rate infusion of
      [U-13C]-palmitate (0.0026 mg kg-1 min-1, primed by a 0.085 mg kg-1 NaH13CO3 bolus) and
      [D2]-glucose (0.0728 mg kg-1 min-1, primed by a 3.203 mg kg-1 D2- glucose bolus) was
      delivered by a Gemini PC2 pump (IMED, San Diego, CA). Preparation of tracers and tracer
      calculations were performed as described.

      Blood and air samples were collected just before start of infusion of the stable isotopes,
      and again after 2, 10, 14, 16, 18, 20, 22 and 24 hours of fasting (figure 1). Gas exchange
      measurements (indirect calorimetry) were performed with a metabolic cart (Cosmed Quark b2;
      Cosmed Srl., Milan, Italy). At the same time-points, expired air was collected in a 15 L
      Douglas bag (Hans Rudolph, Kansas City, MO, USA) and 10 mL samples were transferred to vacuum
      tubes (Vacutainer, BD, Franklin Lakes, NJ, USA) for 13CO2 analysis.

      The blood glucose levels were monitored continuously at all blood sampling times and every
      third hour during the night in the patients. If the subjects developed symptoms of
      hypoglycaemia (fatigue, dizziness, nausea) the blood sugar was measured immediately. The
      fasting period lasted 24 hours or until signs of hypoglycemia as mentioned above or blood
      glucose below 3.0 mmol/L. Patients received an IV bolus of 10% glucose according to weight if
      signs of hypoglycemia occurred.

      Analyses of blood samples and expired 13CO2. Venous blood was transferred to cooled tubes
      with EDTA (Ethylenediaminetetraacetic acid) (0.33M, 10μL mL-1) and spun at 4,000 rpm for 10
      minutes. Plasma was distributed to Eppendorf tubes and immediately frozen on dry ice and
      stored at -80°C until analysis. Plasma insulin and glucagon analyses were performed at the
      Department of Clinical Biochemistry at Rigshospitalet, Copenhagen, Denmark (Cobas 8000,
      Roche, Rotkreuz Switzerland). Plasma free fatty acids and catecholamines were analyzed by
      spectrophotometry (Multiskan GO, Thermo Scientific, SkanIt™ Software, Thermo Fisher
      Scientific Inc., USA). Plasma palmitate, β-hydroxybuturate, acetoacetate, pyruvate, glycerol
      and amino acids as well as 13CO2-breath enrichment were analyzed by gas chromatography
      isotope ratio-mass spectrometry (Thermo Finnigan MAT GmbH, Bremen, Germany). Isotope tracer
      enrichments were determined using gas chromatography-mass spectrometry (Thermo Finnigan MAT
      GmbH, Bremen, Germany).

      Glucose and lactate were analyzed on (ABL 700) immediately as the blood was drawn.

      Shofield equation was used to calculate expected basal metabolic rate for the children: Males
      10-17 years: (17.7 x weight+657+105) and females 10-17 years: (13,4 x weight+692+112) and the
      results were compared with the resting metabolic rate (RMR) measured by indirect
      calorimetric, as described above, at the end of the study, were patients had been resting and
      fasting for more than 8 hours.
    

Intervention name(s): Fasting
Intervention type(s): Other
Intervention description(s): Fasting for 24 hours or until hypoglycemia (blood glucose < 3mmol/L) or symptoms of hypoglycemia
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science