Transplanting fat may treat such inherited metabolic diseases as maple syrup urine disease (MSUD) by helping the body process the essential amino acids that these patients cannot, according to Penn State College of Medicine researchers.

The researchers are targeting maple syrup urine disease because it disproportionately affects the Amish and Mennonites, who reside in the central Pennsylvania communities surrounding the College of Medicine and its hospital, Penn State Milton S. Hershey Medical Center.

The team transplanted up to two grams of fat into either abdomens or backs of mice genetically engineered to have MSUD. When fat was transplanted in the back of the MSUD mice, amino acids levels decreased considerably compared to non-transplanted MSUD mice. The fat was either cut into small pieces or minced into fine pieces, with no noticeable difference in results.

Further research

The procedure does not work in the abdomen and instead resulted in inflammation and the transplanted fat not forming blood vessels or attaching properly.

The procedure may be effective for other inherited metabolic diseases, including phenylketonuria and organic acidurias, said Christopher Lynch, Professor of cellular and molecular physiology, and lead researcher.

‘We’re taking lessons from plastic surgeons to see how much and how best to transplant the fat,’ Lynch said. ‘We found that injecting more fat didn’t mean better results. When we increased the fat injected from 1–2g, it did not lower the amino acid levels further. So injecting less fat may help blood vessels develop through the fat, helping to circulate more of the amino acids through the transplanted tissue.’

Researchers are also looking into the use of adult stem cells mixed with the transplanted fat to help with replenishment. In other kinds of transplants, stem cells also reduce rejection.

Lynch’s team believes that it may be easier to get fat donors compared to other organs and that fat transplant operations would be far less expensive than other kinds of transplants. Alternatively, it could be a bridging therapy before liver transplant.