Stories that caught our eye: smelling weight gain, colon cancer & diet and diabetes & broken bones

How smelling your food could cause weight gain (Karen Ring).
Here’s the headline that caught my eye this week: “Smelling your food first can make you fat…”

It’s a bizarre statement, but the claim is backed by scientific research coming from a new study in Cell Metabolism by researchers at the University of California Berkeley. The team found that obese mice who smelled their food before eating it were more likely to gain weight compared to obese mice that couldn’t smell their food.

Their experiments revealed a connection between the olfactory system, which is responsible for our sense of smell, and how the mice metabolize food into energy. Obese mice that lost their ability to smell actually lost weight on a high-fat diet, burned more fat, and became more sensitive to the hormone insulin. Insulin regulates how much glucose, or sugar, is in the blood by facilitating the absorption of glucose by fat, liver and muscle cells. In obese individuals, insulin resistance can occur where their cells are no longer sensitive to the hormone and therefore can’t regulate how much glucose is in the blood.

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Both mice in this picture were fed the same high-fat diet. The only difference: the lower mouse’s sense of smell was temporarily blocked. Image: UC Berkeley

For obese mice that could smell their food, the same high fat diet given to the “no-smellers” resulted in massive weight gain in the “smellers” because their metabolism was impaired. Even more interesting is the fact that other types of smells unrelated to food, such as the scent of other mice, influenced weight gain in the “smellers”.

The authors concluded that the centers in our brain that are responsible for smell (the olfactory system) and metabolism (the hypothalamus) are connected and that manipulating smell could be a future strategy to influence how the brain controls the balance of energy during food consumption.

In an interview with Tech Times, senior author on the study, Dr. Andrew Dillin, explained how their research could potentially lead to a new strategy to promote weight loss,

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Andrew Dillin. Image: HHMI

“Sensory systems play a role in metabolism. Weight gain isn’t purely a measure of the calories taken in; it’s also related to how those calories are perceived. If we can validate this in humans, perhaps we can actually make a drug that doesn’t interfere with smell but still blocks that metabolic circuitry. That would be amazing.”

A link between colorectal cancer and a Western diet identified
Weight gain isn’t the only concern of a eating a high-fat diet. It’s thought that 80% of colorectal cases are associated with a high-fat, Western diet. The basis for this connection hasn’t been well understood. But this week, researchers at the Cleveland Clinic report in Stem Cell Reports that they’ve pinpointed a protein signaling network within cancer stem cells as a possible source of the link.

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Cancer stem cells have properties that resemble embryonic stem cells and are thought to be the source of a cancer’s unlimited growth and spread. A cancer stem cell maintains its properties by exploiting various cell signaling processes that when functioning abnormally can lead to inappropriate cell division and tumor growth. In this study, the team focused on one cell signaling process carried out by a protein called STAT3, known to promote tumor growth in a mouse model of colon cancer. When the team blocked STAT3 activity, high fat diet-induced cancer stem cell growth subsided.

In a press release, Dr. Matthew Kalady, a colorectal surgeon at the Cleveland Clinic and an author on this study, explained how this new insight can open new therapeutic avenues:

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Matthew Kalady. Image: Cleveland Clinic

“We have known the influence of diet on colorectal cancer. However, these new findings are the first to show the connection between high-fat intake and colon cancer via a specific molecular pathway. We can now build upon this knowledge to develop new treatments aimed at blocking this pathway and reducing the negative impact of a high-fat diet on colon cancer risk.”

 

 

Scientists connect dots between diabetes and broken bones.
Type 2 diabetes carries a whole host of long-term complications including heart disease, nerve damage, kidney dysfunction and even an increased risk for bone fractures. The connection between diabetes and fragile bones has not been well understood. But this week, researchers at New York University of Dentistry, Stanford University and China’s Dalian Medical University published a report, funded in part by CIRM, in this week’s Nature Communications showing a biochemical basis for this connection. The new insight may lead to treatment options to prevent fractures.

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Chemical structure of succinate.
Image: Wikimedia Commons.

Fundamentally, diabetes is a disease that causes hyperglycemia, or abnormally high levels of blood sugar. The team ran a systematic analysis of hyperglycemia’s effects on bone metabolism using bone marrow samples from diabetic and healthy mice. They found that the levels of succinate, a key molecule involved in energy production, are over 20 times higher in the diabetic mice. In turns out that succinate also acts as a stimulator of bone breakdown. Now, bone is continually in a process of turnover and, in a healthy state, the breakdown of old bone is balanced with the formation of new bone. So, it appears that the huge increase of succinate is tipping the balance of bone turnover. In fact, the team found that the porous, yet strong inner region of bone, called trabecular bone, was significantly reduced in the diabetic mice, making them more susceptible to fractures.

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The density of spongy bone, or trabecular bone, is reduced in type 2 diabetes.
Image: Wikimedia commons

Dr. Xin Li, the study’s lead scientist, explained the importance of these new insights for people living with type 2 diabetes in a press release:

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Xin Li.
Image: NYU Dentistry

“The results are important because diabetics have a significantly higher fracture risk and their healing process is always delayed. In our study, the hyperglycemic mice had increased bone resorption [the breakdown and absorption of old bone], which outpaced the formation of new bone. This has implications for bone protection, as well as for the treatment of diabetes-associated collateral bone damage.”

 

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