The drug metformin is not recommended for people with kidney disease. For this reason, some people think that metformin causes kidney disease. But new evidence suggests that metformin might actually protect the kidneys.
For many people with type 2 diabetes, metformin is a very effective drug. In everyone, the liver is a sort of "mother" organ. When blood glucose (BG) levels go down, the liver releases some glucose into the blood to make sure all the other organs get enough glucose energy to work properly.
When you eat and your BG levels start going up, the liver is supposed to stop pushing all this glucose out into the bloodstream.
But for some reason, in people with type 2 diabetes, like an oversolitous mother, the liver doesn't stop feeding the bloodstream after meals. "Eat eat!" I can hear it say to a bloodstream already stuffed with glucose. And this continued release of glucose into the bloodstream after meals is one reason people with type 2 go high after meals.
Metformin helps to stop this process, and this is its main action. But it also reduces insulin resistance. In addition, generic metformin is pretty cheap. So overall, it's a good drug for type 2s or even for type 1s who have developed insulin resistance.
Metformin can also cause side effects, especially gastrointestinal distress. Most people find that these side effects are reduced if they start with a low dose and work up to an effective dose. Taking the drug with meals also helps. Others have found that things like yogurt and milk thistle help with the GI symptoms. The extended-release form seems to cause fewer of these problems.
But for those with kidney disease, metformin is not so great. This is because metformin is excreted through the kidneys. If the kidneys aren't functioning well, the metformin could build up in the body until it reached dangerous levels and caused lactic acidosis, a dangerous condition with a high mortality rate.
But a new study suggests that in people with healthy kidneys, metformin could help to preserve their function. It does this by increasing levels of a molecule known as AMPK (AMP kinase).
The research, led by Kumar Sharma at the University of California at San Diego, concerned an adipokine (a hormone produced by fat cells) called adiponectin. Unlike a lot of the substances produced by fat cells, adiponectin is beneficial. You want your adiponectin levels to be high.
The researchers found that adiponectin suppresses inflammation and reduces the amount of protein in the urine. Protein in the urine is a sign of damaged kidneys.
Mice engineered not to produce adiponectin started releasing protein into their urine. When they gave the mice adiponectin, the protein returned to normal low levels.
The interesting thing for anyone who takes metformin is that they found that adiponectin activated AMPK. And when AMPK was stimulated, the kidney stopped leaking protein.
The researchers noted that certain drugs, including metformin, stimulate AMPK and suggested that adiponectin or metformin could be used to protect kidney function in obese persons, even those who did not have diabetes.
Rosiglitazone (Avandia) also increases adiponectin levels.
They also note that the human studies were done in nondiabetic obese African Americans, and there is not yet any evidence that it would be as beneficial in other groups.
This is just one study, so people shouldn't rush off and take lots of metformin in the hopes of preserving kidneys. But it does suggest that we shouldn't worry that metformin will harm our kidneys.
Read Dr. Bill Quick's post, "Metformin and the Risk of Lactic Acidosis," for more information on Metformin and kidneys.