The Danes injected plasmids containing synthetic EPO-genes once into the tibialis cranialis [calf muscle] of mice. At the same time they subjected the mice to electric shocks to improve the cells’ uptake of the new genes. Then they looked at whether the animals became better at burning fat. Evidence from hospitals – and from chemical cyclists, although the researchers don’t mention these – indicates that EPO may enhance energy burning. This evidence inspired the researchers to assess whether EPO [structure above] may perhaps be an interesting ingredient for weight-loss medication.
After treatment, the concentration of EPO in the mice increased by a factor of 60. And the increase of the EPO concentration in the calf muscle was 500 times higher than in the blood.
This abnormal EPO level changed the way in which the mice reacted to a high fat diet. They also became less fat. The figure below shows the effect of the synthetic genes on the amount of abdominal fat. The mice that were on a healthy diet also lost significant amounts of fat.
The synthetic genes also caused an increase in muscle mass in the mice, especially in the tibialis cranialis, but also in the same muscle in the other leg of the animals.
The increase in muscle mass is probably the result of new blood vessels being created in the muscles as a result of high EPO levels.
The cellular metabolism changes in the muscle. Sensitivity to insulin increases and the concentration of glucose in the blood decreases. The muscle cells become more efficient at burning fat, as the figure below shows.
The researchers think they may be on the way to a new treatment for obesity, but suspect that the current substances are not suitable. An abnormally high EPO level is not very healthy: the blood becomes so thick that the risk of heart attack increases. But the Danes are predicting the development of “EPO versions to counteract metabolic syndrome without exacerbated and undesired hematocrit increase”.
Erythropoietin Over Expression Protects against Diet-Induced Obesity in Mice through Increased Fat Oxidation in Muscles
Erythropoietin can be over-expressed in skeletal muscles by gene electrotransfer, resulting in 100-fold increase in serum EPO and significant increases in haemoglobin levels. Earlier studies have suggested that EPO improves several metabolic parameters when administered to chronically ill kidney patients. Thus we applied the EPO over-expression model to investigate the metabolic effect of EPO in vivo.
At 12 weeks, EPO expression resulted in a 23% weight reduction (P<0.01) in EPO transfected obese mice; thus the mice weighed 21.9±0.8 g (control, normal diet,) 21.9±1.4 g (EPO, normal diet), 35.3±3.3 g (control, high-fat diet) and 28.8±2.6 g (EPO, high-fat diet). Correspondingly, DXA scanning revealed that this was due to a 28% reduction in adipose tissue mass.
The decrease in adipose tissue mass was accompanied by a complete normalisation of fasting insulin levels and glucose tolerance in the high-fat fed mice. EPO expression also induced a 14% increase in muscle volume and a 25% increase in vascularisation of the EPO transfected muscle. Muscle force and stamina were not affected by EPO expression. PCR array analysis revealed that genes involved in lipid metabolism, thermogenesis and inflammation were increased in muscles in response to EPO expression, while genes involved in glucose metabolism were down-regulated. In addition, muscular fat oxidation was increased 1.8-fold in both the EPO transfected and contralateral muscles.
In conclusion, we have shown that EPO when expressed in supra-physiological levels has substantial metabolic effects including protection against diet-induced obesity and normalisation of glucose sensitivity associated with a shift to increased fat metabolism in the muscles.