ICE/ENDO 2014: 16th International Congress of Endocrinology and The Endocrine Society's 96th Annual Meeting:
Can Vitamin D Help Control Weight and Blood Glucose?
“Low Vitamin D levels are consistently associated with obesity, type 2 diabetes, and cardiovascular disease, yet no one understands if low Vitamin D levels are actually linked to the onset of obesity or linked to the progression of type 2 diabetes,” stated Stephanie Sisley, MD during her presentation on June 22, 2014 at The Endocrine Society Annual Meeting in Chicago, IL. Dr. Sisley is Assistant Professor at Baylor College of Medicine in Houston, TX.
Role of the Hypothalamus
The brain’s hypothalamus is vitally important in regulating weight; it takes signals from the body that tells it what the body’s nutrient status is and regulates food intake and energy expenditure to maintain a steady body weight. In obesity, these processes are dysregulated, and because the brain is unable to sense what is happening in the body, weight, food intake, and energy expenditure is not controlled.
Dr. Sisley stated, “It’s highly likely a Vitamin D deficiency is linked to the cause of obesity, but this action is actually through the brain, and the Vitamin D receptor, which is the only receptor known to actually control Vitamin D’s effects, is present in the brain.”
Vitamin D and Weight Control?
The purpose of Dr. Sisley’s study was to answer the question, “Can Vitamin D act in the brain to control weight?” It is known that Vitamin D has limited transport across the blood-brain barrier, and is known to affect calcium in the body. Using Long-Evans rats, Vitamin D was delivered directly into the brain through a stainless steel cannula into the third ventricle, which is surrounded by the hypothalamus. A mini osmotic pump was implanted beneath the skin and connected to the cannula. The rats were fed a 45% high-fat diet, which induced obesity for eight weeks. The active form of Vitamin D (1,25-Dihydroxyvitamin D) was delivered into the rats for four weeks.
- The results of four weeks of continuous Vitamin D3 treatment caused a significant reduction in body weight, which was secondary to fat mass loss.
- The rats did not lose muscle mass.
- The rats seemed to eat less with the Vitamin D3 treatment than those that did not receive D3 (comparative vehicle).
- The study demonstrated that Vitamin D can act in the brain to control weight.
Vitamin D and Glucose Control?
The next question was, “Can Vitamin D act in the brain to control glucose?” “We focused on the brain even though Vitamin D is known to affect islet cells and create insulin secretion. This same area of the brain that’s important in weight regulation is also very important in controlling glucose. We hypothesized that Vitamin D may be acting in the brain to control glucose levels," Dr. Sisley explained.
By performing glucose tolerance tests, it was determined that Vitamin D in the brain could improve glucose tolerance.
Using Long-Evans rates, obesity was induced, and through a catheter in the jugular vein and carotid artery, insulin and glucose were painlessly delivered, and blood withdrawn. Next, a glucose clamp was utilized to maintain blood glucose at a steady rate. “With Vitamin D3 treatment in the brain, the animals needed more glucose. This means the insulin was working better in these animals, and we consider that an improvement in insulin sensitivity,” stated Dr. Sisley.
To summarize, Dr. Sisley made the following remarks about the study data:
- Vitamin D can act in the brain to decrease body weight, fat mass, and food intake.
- Vitamin D can act in the brain to improve glucose tolerance and insulin sensitivity, specifically at the level of the liver.
“We know very little though about how Vitamin D can act in the brain. We need further research to define the mechanisms, including how Vitamin D actually crosses the blood-brain barrier, and how these processes might be dysregulated in obesity,” concluded Dr. Sisley.
New research could lead to the creation of new drugs to target specific processes, deliver more effective care, and achieve the ultimate goal of personalized medicine.