Insulin and Potassium

Insulin has a number of actions on the body besides lowering your blood glucose levels.  Insulin suppresses the breakdown and buildup of glycogen, which is the storage form of glucose, it blocks fat metabolism and the release of fatty acids, and it puts potassium into the cells by activating the sodium-potassium cellular channels.  Insulin stimulates the uptake of glucose and potassium in all cells of the body but primarily fuels the muscle cells as well as some of the fat cells.

In type 2 diabetes or metabolic syndrome (a form of metabolic disease), insulin is not functioning up to its normal level.  The cells of the body become resistant to insulin and the blood sugar levels are elevated.

The serum potassium (K+) level is a reflection of the total body stores of potassium, although it can be inaccurate in some conditions that affect the distribution of potassium in the body’s cells.  The plasma potassium level determines the resting potential of the cells of the body.  A person can have low potassium (hypokalemia) or high potassium (hyperkalemia), both of which are asymptomatic conditions that can be serious as they both cause heart arrhythmias.

The Relationship between Insulin and Potassium

Shortly after insulin was discovered, scientists revealed that insulin had something to do with the potassium levels in both the cells and in the blood.  The insulin is the hormone in the body that keeps the potassium level in the blood within the normal range.  When insulin is decreased, the potassium level rises and can rise even further if you eat something high in potassium, such as salt substitutes and bananas.

When the potassium level is high, it causes the pancreas to release insulin in order to counteract the effects of high potassium levels.  When you eat something that is high in potassium, the potassium enters the blood stream, increases the potassium level, stimulates insulin to be released, and then is put into the cells along with glucose.  When all of this works normally, most of the potassium in the body is inside the cells and very little of it is circulating in the bloodstream.

Patients with diabetes often have high potassium levels.  Type 1 diabetics have extremely low levels of insulin secreted by the pancreas and are at risk for having hyperkalemia (high K+ levels).  Without the insulin, the potassium cannot enter the cells and more of the potassium is allowed to float around in the blood.

Potassium is the main cation (positively charged molecule) in the cells.  Potassium is required to keep the water in the cells so they don’t become dehydrated.  Even when type 1 and type 2 diabetics have their blood sugars well managed, there is some type of problem with the kidneys that prevents potassium excretion because the tubules inside the kidneys are insensitive to the hormone known as aldosterone.

Research studies have been done looking at whether the uptake of glucose into the cells is connected to the potassium uptake.  Are the two molecules dependent on one another in order for uptake of the molecules into the cells?   According to some research, the answer is yes.  People who are insulin-deficient also have a blockage in the uptake of both potassium and glucose.

Other research, however, disputes this and indicates that the uptake of glucose doesn’t have to be related to the uptake of potassium, even though both require adequate amounts of insulin in order to be put into the cells.

How does insulin work. Insulin regulates the metabolism and is the key that unlocks the cell's glucose channel

How does insulin work. Insulin regulates the metabolism and is the key that unlocks the cell’s glucose channel

The Results of One Study

One study looked at 45 participants.  Some had type 2 diabetes, while others were normal.  Only those diabetics that required insulin or were treated with thiazolidinediones were excluded from the study.  Each diabetic patient was treated with either metformin, a sulfonyl urea medication, or a combination of the two. They all ate a specific diet for 8 days and, prior to being tested, drank 300 cc of water at bedtime the night before the test.

On the ninth day, the participants were fasting and underwent a test involving the infusion of insulin for two hours.  After the insulin was started, each participant was also given IV glucose within 4 minutes of starting the insulin in order to keep the glucose levels as stable as possible.  The plasma insulin level was checked along with the levels of potassium and glucose at the beginning and the end of the insulin in fusion.

The researchers were looking at how much the potassium fell when the participants were given both glucose and insulin for two hours.  They also measured the amount of phosphate in the bloodstream before and after the 2-hour test.

The diabetic participants had higher insulin levels in their bloodstream when compared to those who didn’t have diabetes but not by much.  The diabetic participants had higher glucose levels as well.   The levels of creatinine, phosphate, and potassium were the same in both groups.

At the end of the study, type 2 diabetics had more insulin resistance when compared to the normal participants.  The more the diabetic person weighed, the greater was their level of insulin resistance. Potassium and phosphate levels, however, were not related to the weight of the participant.

Both the diabetics and nondiabetics had a reduction in potassium when insulin and glucose were given.  There appeared to be no relationship between the insulin resistance and the fall in potassium and phosphate levels, however.

The Study’s Conclusion

The study concluded that insulin was responsible for the uptake of both glucose and potassium in the cells but that there were two different mechanisms involved in the uptake of these molecules.  Glucose levels were harder to bring into the normal range in diabetic participants when compared to non-diabetics but both groups were able to bring potassium into the cells at about the same rate.

Insulin resistance, therefore, seems to be connected only to the uptake of glucose in the cells but the uptake of potassium into the cells by type 2 diabetics is the same, even if the participant had abnormal glucose uptake. From this, they concluded that, while insulin has the two functions of putting glucose and potassium into the cells, it does so using two different mechanisms of action.  The body appears to have some mechanism of keeping the potassium level in a normal range that is unrelated to its ability to keep the glucose in the normal range.

This is good for diabetics because it means that, even when the blood glucose levels are out of control, the mechanisms to keep potassium levels from being too high in the bloodstream are normal.  The people at the highest risk of having both elevated potassium levels and elevated blood sugar levels together are type 1 diabetics, who lack insulin to do put both potassium and glucose into the cells. insulin has several physiologic actions that include stimulation of cellular glucose and potassium uptake. The ability of insulin to induce glucose uptake by cells is impaired in type 2 diabetes mellitus, but whether potassium uptake is similarly impaired is not known. This study examines whether the cellular uptake of these molecules is regulated in concert or independently.

References:

  1. Nguyen TQ, et al.  Comparison of Insulin Action on Glucose versus Potassium Uptake in Humans. Clin J Am Soc Nephrol. 2011 Jul; 6(7): 1533-1539.
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