The Val103Ile polymorphism of melanocortin-4 receptor regulates energy expenditure and weight gain.
OBJECTIVE
The melanocortin-4 receptor (MC4R) regulates energy intake. On the basis of animal studies, it may also regulate energy expenditure.


METHODS
The effect of the Val103Ile polymorphism of the MC4R gene on energy metabolism was studied in 229 middle-aged nondiabetic subjects (Group 1, age 51.2 +/- 9.8 years, BMI 26.8 +/- 4.5 kg/m2) and on weight gain in 1013 elderly subjects (Group 2, age 69.9 +/- 2.9 years, BMI 27.4 +/- 4.1 kg/m2) during a 3.5-year follow-up study. In Group 1, insulin sensitivity, energy expenditure, and substrate oxidation were measured with the hyperinsulinemic euglycemic clamp combined with indirect calorimetry.


RESULTS
In Group 1, the Val103Ile genotype was associated with high rates of energy expenditure (63.42 +/- 13.40 in eight subjects with the Val103Ile genotype vs. 59.86 +/- 7.33 J/kg per minute in 221 subjects with the Val103Val genotype, p = 0.007), high rates of glucose oxidation (8.90 +/- 6.15 vs. 6.07 +/- 4.38 micromol/kg per minute, p = 0.020), and low levels of free fatty acids (0.45 +/- 0.18 vs. 0.56 +/- 0.23 mM, p = 0.029) in the fasting state, and with high rates of glucose oxidation during the clamp (18.88 +/- 4.63 vs. 17.60 +/- 3.24 micromol/kg per minute, p = 0.031). In Group 2, the 103Ile allele was associated with an increase in weight gain during the follow-up (0.78 +/- 3.98 vs. -0.82 +/- 3.98 kg, p = 0.038).


CONCLUSIONS
The Val103Ile polymorphism of the MC4R gene is associated with energy expenditure in humans. Furthermore, it may associate with glucose oxidation, free fatty acid levels, and weight gain.
Rutanen
Jarno
J
Department of Medicine, Kuopio University Hospital, PB 1777, 70211 Kuopio, Finland.
Pihlajamäki
Jussi
J
Karhapää
Pauli
P
Vauhkonen
Ilkka
I
Kuusisto
Johanna
J
Moilanen Mykkänen
Leena
L
Laakso
Markku
M
D000328:Adult; D000368:Aged; D000483:Alleles; D001786:Blood Glucose / Q000378:metabolism; D002153:Calorimetry, Indirect; D004734:Energy Metabolism / Q000235:genetics*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005387:Finland; D005787:Gene Frequency; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D007532:Isoleucine / Q000235:genetics*; D008875:Middle Aged; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D011446:Prospective Studies; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics* / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014633:Valine / Q000235:genetics*; D015430:Weight Gain / Q000235:genetics*
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D044105:Receptor, Melanocortin, Type 4; D007532:Isoleucine; D014633:Valine