Move over sugar? Fats and proteins can trigger bigger insulin responses than glucose

Not everyone responds the same way to carbohydrates, fats or protein. In fact, it turns out that some individuals have bigger insulin responses to either proteins or fats than they do to glucose.This was the unexpected finding in a study by Canadian researchers in Cell Metabolism.“We generally think of ‘sugars’ as being the strongest insulin-release stimuli, so this was very surprising to us. So much so that we did not believe it the first few times we saw it,” said study coauthor Jelena Kolic, a postdoctoral fellow in the James Johnson Lab at the University of British Columbia's faculty of medicine. While it has long been established that glucose is the major driver of insulin secretion, the researchers were curious as to how much proteins and fats could module response. It’s an area that hadn’t been widely explored. But there had been some clues. For one, it was known that individuals can respond differently to different diets. Plus, there is high variability between people in terms of their responses to even just the one macronutrient: glucose, the paper said.The idea that the amount of insulin released from insulin-producing islets could be significant from other types of food or macronutrients was a new one.And so, a study was created to explore this. The researchers used Islets of Langerhans cells harvested from the pancreas of 140 cadavers. The islets came from the Alberta Diabetes Institute IsletCore. The cadaver samples were from a mix of people with a history of diabetes, a family history of diabetes or no diabetes. Most were from non-diabetics. A total of 17 of the organ donors had T2D diagnosis, according to their families. “For some of the donors, the families also provided lists of diabetes medications the donor was on. This supported the available HbA1c measurements, which were elevated, for the majority of the donors as well,” Dr. Kolic told the Medical Post. The other 123 donors studied did not have any family-declared diabetes. The researchers systematically measured insulin secretion in response to carbohydrates, which consisted of 15 or 6 mM of glucose; an amino acid consisting of 5 mM leucine; and fatty acids which consisted of 1.5 mM of an oleate and palmitate mixture. Each islet sample was tested with separate exposures to each of the three nutrients. The majority of donors’ islets had the biggest insulin response to glucose, moderate response to amino acid, and minimal response to fatty acid. However, 9% of donors’ islets had bigger responses to amino acids, and 8% had the biggest response to the fatty acids. These responses were larger than their glucose-stimulated insulin responses.Those that secreted more insulin in response to leucine than to high amounts of glucose were more likely to have been diagnosed with T2D, but there was no difference in HbA1c between the high and low responders. As for the fat or lipid-hyper-responsive islets, these donors had higher HbA1c. But there were no other significant differences in islet isolation or culture parameters seen between them and those who responded more to glucose.“Expectedly, high HbA1c was negatively correlated to insulin secretion stimulated by high glucose,” the paper said.Also surprisingly, donor BMI had only minor effects on macronutrient stimulated insulin secretion. As for clinical implications, Dr. Kolic stated “we do hope to collaborate with clinical researchers in the future, to see if and how our findings . . translate into living people.” If the findings pan out, it could majorly influence how dietary recommendations for individuals are made. “Instead of using a one-size-fits-all approach when it comes to diet recommendations, once we better understand why and how to fine-tune an individual’s insulin release in response to a specific nutrient, we should be better able to tailor an individual’s diet. (That is) in the context of blood sugar control and weight loss,” she said.Dr. David Jenkins, a professor of medicine and nutrition science at the University of Toronto, also found the results unexpected. He was not involved in the study, but stated that the big surprise is that for some of the people the biggest effect was from fat.“The protein responses are interesting and we are advising our patients with diabetes to increase plant protein foods intake in line with Canada’s Food Guide,” he said.He found that the fat effect is ‘strange’ and wondered if it could be dependent on fatty acid type? Or “Could it be an 8% experimental deviation?”

Move over sugar? Fats and proteins can trigger bigger insulin responses than glucose

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