Leptin reverses lipodystrophy in diabetic patients
Researchers have successfully used the hormone leptin to treat patients suffering from lipodystrophy.
The findings by scientists at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and the University of Texas Southwestern Medical Center appear in the 21st February 2002, issue of the New England Journal of Medicine. “This is the first example of leptin’s use in a therapeutic role in a rare form of diabetes,” says NIDDK’s Phillip Gorden, MD, the study’s senior investigator.
People with lipodystrophy have few or no fat cells and thus lack leptin, a hormone produced by and stored in fat cells. Because they have no fat cells, people with the condition usually store huge amounts of lipids (fat) in inappropriate places like muscle or liver, and they have extremely high levels of lipids in their blood. These patients are likely to be insulin resistant, meaning their bodies don’t readily respond to insulin, the hormone that allows muscle and fat cells to use glucose properly. The condition can be congenital or acquired.
Eight of the nine female patients who participated in the study had diabetes and were taking either insulin or a diabetes drug, or a combination of the two. During the four-month study, most patients experienced significant improvements in levels of fasting glucose, haemoglobin A1c, which measures a person’s average blood glucose over the three previous months, and triglycerides. Patients were able to reduce or stop using insulin and drugs to control their diabetes, and they reported eating less following treatment. The findings suggest that leptin reduces insulin resistance and prevents the body from accumulating fat in the wrong places.
“It is too soon to make the assumption that leptin will be useful in typical type 2 diabetes,” says Gorden. Although people with lipodystrophy and type 2 diabetes can develop some of the same complications when blood glucose is uncontrolled, the two conditions differ in fundamental ways. Most people with typical type 2 diabetes are overweight and not deficient in leptin. In fact, their leptin levels are usually high, and they may be resistant to leptin’s effects, says Gorden.
The rationale for treating lipodystrophy with leptin comes from classical endocrinology. “The idea is that if people have a hormone deficiency and they are given replacement hormone, they should respond,” says Gorden.
“What we have shown is that in a leptin-deficient state, we can correct many of the abnormalities that come with it,” adds Elif Arioglu Oral, MD, the paper’s lead author and a former research fellow at NIDDK. The results also suggest that leptin deficiency may explain the insulin resistance seen in people with lipodystrophy. “For the first time, we’re seeing leptin working as an insulin-sensitising agent,” adds Oral, now an assistant professor at the University of Michigan in Ann Arbor. Earlier leptin studies showed that lack of the hormone caused obesity in mice; resistance to leptin likewise contributed to obesity in mice and humans.
For all patients, average fasting triglyceride levels dropped by approximately 60% and liver volume dropped by 28%. The normal range for plasma triglycerides is 35 to 155 mg/dL. The level for patients at the start of the study ranged from 445 to 9,560. At the study’s conclusion, the range was 123 to 1,214.
The change in the patient with the highest triglyceride level was dramatic, says Oral. No medications had worked for this patient. The extra lipid had deposited in the skin, causing a lot of pain, and her liver was very enlarged. To remove the triglycerides, every week she had to go through aphaeresis, a process where blood is removed, components are separated out, and the blood is returned to the body. “Within three months of leptin therapy her liver had shrunk, and she was off aphaeresis,” says Oral. “Treatment made a difference in her quality of life.”
Estrada and colleagues have previously described significantly lower plasma leptin levels in HIV-infected lipoatrophic patients than in healthy control individuals (J Acquir Immune Defic Syndr 2002 Jan 1;29(1):32-40). Perhaps leptin therapy in these individuals might also be of benefit?
Oral EA, Simha V, Ruiz E et al. Leptin-replacement therapy for lipodystrophy. N Engl J Med 2002 Feb 21;346(8):570-8.
Source: NIH press release