In mice on a high-fat diet, turning off insulin's signal in the kidney doesn't change blood pressure or salt balance — meaning insulin in the kidney might not be needed to hold onto salt when obesity is caused just by diet.

When scientists turned off insulin's signal in the kidney tubes of obese, insulin-resistant mice, the mice didn't hold onto salt as much — showing that insulin in the kidneys helps control salt balance in obesity.

Insulin makes your kidneys hold onto salt, even if you're not eating much of it.

When scientists turned off insulin's signal in the kidneys of obese, insulin-resistant mice on a certain hormone, the mice started spilling a lot of sugar in their urine—way more than normal—showing that insulin in the kidneys helps control how much sugar gets reabsorbed.

In mice with obesity and high blood pressure caused by a hormone called fludrocortisone, turning off the insulin receptor in the kidney's tubules only slightly lowers blood pressure—by about 2.3 points—suggesting insulin in the kidneys plays a small role in raising blood pressure here.

If your body has too much insulin for a long time, it can make your kidneys hold onto more salt, which increases your blood volume and raises your blood pressure—even if you're not eating too much salt.