The gut isn't just about digestion. It has a significant say in our overall health,it is an important part of the immune system and influences our metabolism. To better understand the complexity of these relationships, we invited Prof. Dr. Florian Kiefer, an endocrinologist and internationally recognized metabolism expert, for an interview. Join Prof. Dr. Kiefer on an interesting journey through the connections between the microbiome, immune system, fat cells, and metabolism, and learn new things about the importance of your own gut health.
Prof. Kiefer, could you provide an overview of your current clinical work and research activities?
“In my clinical practice, I frequently see patients with metabolic disorders such as obesity and diabetes, as well as hormonal imbalances and digestive problems. These diseases are on the rise, partly due to unfavorable lifestyle and dietary habits, including increased consumption of energy-dense processed foods, and partly due to changes in the environment, including occupational, societal, and psychosocial factors. In the case of obesity or adiposity, we often refer to an 'obesogenic environment' as a habitat that promotes obesity. One of my research focuses is on exploring mechanisms that can mitigate metabolic disorders like obesity. My research group has a keen interest in brown adipose tissue, a type of healthy fat that, unlike the more common white adipose tissue, can burn energy in the form of heat and thereby positively affect metabolism. It's very exciting that the microbiome also appears to have an influence on the activity of brown adipose tissue, which is an aspect we are currently studying as well.”
How important is the microbiome and gut health for our metabolism?
“Interestingly, the microbiome plays a significant role in metabolic disorders such as obesity and diabetes. Numerous studies have shown that there are pronounced changes in the gut flora in these conditions, with the suspicion that the unfavorable bacterial composition in the gut also promotes the progression of metabolic diseases. Obesity is often associated with impaired gut permeability, known as 'leaky gut.' This means that gut bacteria or the toxins they produce (endotoxins) can more easily enter the bloodstream from the gut. The cells of the intestinal wall also have an important immune barrier function, which is disrupted in 'leaky gut.' It has recently been shown that in obesity, endotoxins that enter the fat tissue from the gut through the bloodstream disrupt the function of fat cells and inhibit the conversion into metabolically active 'good' brown fat cells. Additionally, the disturbed gut flora in obesity seems to have an impact on nutrient absorption in the gut, with a greater uptake of high-energy dietary fats, which can promote weight gain.
On the other hand, a healthy gut flora also has many protective functions. Numerous gut bacteria produce substances such as short-chain fatty acids, vitamins, and anti-inflammatory compounds that have a positive effect on metabolism and the immune system, suppressing inflammatory reactions. Furthermore, our gut communicates with the brain (the so-called 'gut-brain' axis), where the microbiome also plays an important role. Some gut bacteria produce substances that influence appetite regulation in the brain, potentially prolonging the feeling of fullness after a meal.
Especially when the proportion of these beneficial gut bacteria is reduced due to diseases or poor dietary habits - a condition also known as dysbiosis - it can have detrimental effects on the entire organism.”
What are the unique properties of Lactobacillus plantarum?
“Lactobacillus plantarum (L. plantarum) is a lactic acid-producing bacterial species known for its range of health-promoting effects. It is one of the most extensively studied probiotic bacteria and is considered particularly adaptable. It can produce substances called bacteriocins, which inhibit the growth of other bacteria in its environment. L. plantarum is therefore also used in the food industry for preservation. In foods, this lactic acid bacterium is mainly found in fermented products.
In medicine, L. plantarum holds a significant place in the management of conditions such as irritable bowel syndrome, diarrheal diseases, or chronic inflammatory bowel diseases, as its use can lead to relief from abdominal pain, bloating, and regulation of stool frequencies. In this context, the anti-inflammatory and immunomodulatory effects of L. plantarum in the gut appear to play a role. From a metabolic perspective, it is particularly interesting that the consumption of L. plantarum can support weight loss in overweight individuals, especially by reducing harmful deep abdominal fat (visceral fat), which in turn improves insulin resistance. In animal studies, the intake of L. plantarum has been shown to improve blood sugar levels in diabetic mice and reduce fatty liver in overweight rats. Improvement in blood lipids such as cholesterol and triglycerides has also been reported repeatedly.”
What distinguishes probiotics from postbiotics?
“Changes in the microbiome or colonization of the gut with harmful bacteria can be both a consequence and a cause of diseases. Probiotics are living microorganisms (such as bacteria) that have health benefits for the host. They are found in certain foods and are also used as dietary supplements or medications for the prevention or treatment of diseases. Since they are living organisms, caution must be exercised in the use of probiotics due to the risk of systemic colonization in people with very severe illnesses or weakened immune systems.
On the other hand, postbiotics are not living organisms but rather substances produced by prebiotics. They can be obtained through inactivation (e.g., heat treatment) of prebiotic bacteria. Postbiotics have similar health benefits to prebiotics and may even surpass them in some cases. Moreover, they are considered safer and more stable than live bacteria. This explains why scientific interest in postbiotics has drastically increased in recent years.”
Do postbiotics have an effect on diabetes?
“Although there are currently only limited clinical data on postbiotics and diabetes, animal studies are yielding very promising results. For instance, treatment with heat-inactivated L. plantarum in mice with stress-induced type 2 diabetes leads to an improvement in blood sugar levels and a decrease in fat mass. Other postbiotics have also been shown to lower blood sugar and insulin resistance in animal experiments. So, it is likely only a matter of time until concrete data on the effects of postbiotics in humans with diabetes become available.”
What future scientific developments and health trends related to the microbiome do you anticipate?
“In recent years, we have witnessed an enormous increase in scientific publications on the topics of microbiome, probiotics, and postbiotics. However, we still have much to learn, such as how changes in the microbiome trigger or worsen diseases. We need larger studies conducted over longer periods to better understand the influence of environmental factors, age, and lifestyle on the microbiome and to potentially define microbiome 'standards' within a population group, if such standards even exist. Thanks to technological advancements, such analyses have become significantly easier and more cost-effective.
Regarding probiotics and postbiotics, I hope to see more controlled clinical studies in order to better assess specific effects on certain diseases in humans. One potential future development is the emergence of 'smart' bacteria that are genetically modified to perform certain functions in our bodies, such as combating other pathogens or early detection of tumor diseases. There are already initial examples from this research field known as 'microbial engineering.”