Calpain 3 gene expression in skeletal muscle is associated with body fat content and measures of insulin resistance.
OBJECTIVE
To investigate whether skeletal muscle gene expression of calpain 3 is related to obesity and insulin resistance.


METHODS
Cross-sectional studies in 27 non-diabetic human subjects and in Psammomys obesus, a polygenic animal model of obesity and type 2 diabetes.


METHODS
Expression of CAPN3 in skeletal muscle was measured using Taqman fluorogenic PCR. In the human subjects, body composition was assessed by DEXA and insulin sensitivity was measured by euglycemic-hyperinsulinemic clamp. In Psammomys obesus, body composition was determined by carcass analysis, and substrate oxidation rates, physical activity and energy expenditure were measured by whole-body indirect calorimetry.


RESULTS
In human subjects, calpain 3 gene expression was negatively correlated with total (P = 0.022) and central abdominal fat mass (P = 0.034), and with blood glucose concentration in non-obese subjects (P = 0.017). In Psammomys obesus, calpain 3 gene expression was negatively correlated with circulating glucose (P = 0.013) and insulin (P = 0.034), and with body fat mass (P = 0.049). Indirect calorimetry revealed associations between calpain 3 gene expression and carbohydrate oxidation (P = 0.009) and energy expenditure (P = 0.013).


CONCLUSIONS
Lower levels of expression of calpain 3 in skeletal muscle were associated with reduced carbohydrate oxidation and elevated circulating glucose and insulin concentrations, and also with increased body fat and in particular abdominal fat. Therefore, reduced expression of calpain 3 in both humans and Psammomys obesus was associated with phenotypes related to obesity and insulin resistance.
Walder
K
K
Metabolic Research Unit, School of Health Sciences, Deakin University, Geelong, Victoria, Australia. walder@deakin.edu.au
McMillan
J
J
Lapsys
N
N
Kriketos
A
A
Trevaskis
J
J
Civitarese
A
A
Southon
A
A
Zimmet
P
P
Collier
G
G
D000273:Adipose Tissue; D000328:Adult; D000818:Animals; D001706:Biopsy; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D015992:Body Mass Index; D002153:Calorimetry, Indirect; D002154:Calpain / Q000235:genetics*; D004734:Energy Metabolism; D005260:Female; D015870:Gene Expression; D005849:Gerbillinae; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D016133:Polymerase Chain Reaction
D001786:Blood Glucose; D007328:Insulin; D002154:Calpain