Prior studies in mice have shown that whole body vibration (WBV) can mimic some of the positive effects on health of exercise, and even reverse some of the symptoms of type 2 diabetes. New research by a team at the Medical College of Georgia (MCG) and Dental College of Georgia (DCG) at Augusta University has provided new clues as to the mechanisms involved. Their studies in a mouse model of obesity showed that WBV results in increased levels of inflammation-suppressing immune system macrophages, and high numbers of gut bacteria that makes short-chain fatty acids (SCFAs), which can help the body better utilize glucose.
The findings “… support the notion that WBV has the potential to alter the microbiota in a way that triggers innate and mucosal immunity to produce anti-inflammatory responses, down-regulating the hyper-inflammatory state and reversing the adverse consequences,” the investigators wrote in their published paper in the International Journal of Molecular Sciences. “More studies are required to solidify this novel approach, which can be a very affordable and effective therapeutic modality in the prevention and treatment of many diseases, including diabetes and obesity.” The researchers, headed by Jack Yu, MD, chief of pediatric plastic surgery at MCG, and Babak Baban, PhD, immunologist and intern associate dean for research at DCG, reported their findings in a paper titled, “Whole Body Vibration-Induced Omental Macrophage Polarization and Fecal Microbiome Modification in a Murine Model.”
The combination of high-fat, sugar-heavy diets and “massively reduced physical activities” is largely responsible for what the researchers called “an epidemic of obesity and chronic metabolic diseases,” including type 2 diabetes. Chronic inflammation is a major contributory factor to the development of metabolic and cardiovascular diseases, and the immune system’s macrophages play a key role in regulating inflammatory responses.
The potential to use WBV alongside more conventional measures for improving musculoskeletal health, and also potentially to impact on metabolic diseases such as diabetes and hypertension is gaining scientific interest, the authors continued. “Despite a certain level of controversy, all studies generally support the notion that WBV may improve the inflammatory indices and help to re-establish the immune balance and homeostasis.” However, they acknowledged, the mechanisms involved aren’t clear. “While the biochemical and physiological improvements from WBV as an exercise mimetic are indisputable, how WBV achieves such effects is likely multi-faceted and largely unknown.”
There are two types of macrophage. Those classified as M1 promote inflammation, while M2 macrophages suppress inflammation and play a key role in regulating inflammatory responses. Complex regulatory systems are involved in control glucose utilization, and research has implicated macrophages in feedback loops that foster inflammation and exacerbate insulin resistance and an inability to control glucose levels. The inflammatory status of macrophages also influences the gut microbiome, and the gut microbiome can impact on inflammatory responses, so the immune system and gut microbiome have what the investigators call “an intimate and reciprocal relationship, in that microbiota affects innate immunity and vice versa.”
Back in 2012, Yu reported at the Third World Congress of Plastic Surgeons of Chinese Descent that whole body vibration could reduce some of the effects of diabetes, such as excess urine production and excessive thirst. Those studies were in a mouse model that mimicked overeating adolescents. WBV also reduced inflammation levels, including shifts in some immune cell counts, and was more effective than drugs at reducing A1C (glycated haemoglobin), which is used as a measure of blood sugar levels.
For their newly reported studies, the scientists designed a series of tests in a leptin-deficient mouse model of diabetes to investigate whether WBV led to changes in macrophage type in blood and fat tissue, and/or changes to the gut microbiome. The results showed that WBV increased the numbers of M2 macrophages in both the diabetic and control mice, and restored M2 levels to those of normal controls. These results were “… consistent with our hypothesis that WBV induces macrophage polarization to M2 type in a diabetic mouse model,” the team wrote. WBV was also associated with increased levels of anti-inflammatory molecules including the cytokine IL-10, which were increased in both the diabetic and normal mice after vibration.
A program of six weeks of WBV (20 minutes per day, five days a week) was linked with changes to microbial composition and diversity. Overall microbial diversity decreased, but there was a major increase in Alistipes bacteria, which are normally only found in very small numbers in the microbiomes of healthy laboratory mice. Alistipes are non-alcoholic fermenters that produce SCFAs such as butyrate and acetoacetate, which are “known to be fuel for the gut flora, highly anti-inflammatory, and capable of reversing adverse effects of a high-fat diet.”
The team noted that while it is greater, rather than reduced microbiobial diversity that is thought to be beneficial to health, the reduced microbial diversity in WBV-treated mice may have resulted from an increase in beneficial species of bacteria that produce SCFAs rather than ethanol. Interestingly, Alistipes bacteria have been found in the gut microbiomes of hibernating mammals that undergo extensive nutritional and microbiological adaptations during the winter months.
The researchers claim that their study is the first to document crosstalk between the microbiome and innate immunity by altering the macrophage mix. What isn’t yet known is whether it’s the microbiome changes or the shift in macrophage type that comes first. “The sequencing of the WBV effects is still unclear,” they wrote. “Is M2 polarization antecedent to intestinal microbiome changes or vice versa? One of the next steps that may help to answer that question may be to carry out WBV tests in models in which macrophages are deleted.
“The sequencing is not yet completely clear,” Yu said, “but it appears to be a closed loop, feed forward, self-magnifying cycle.”