[The physiological role of growth hormone and insulin-like growth factors]

The existence of insulin-like growth factors (IGFs) was recognized in connection with the stimulation of sulfate incorporation into cartilage. IGFs take part in the embryonal development and postnatal growth, in interaction with the growth hormone (GH). The physiological effects of IGF1 are promotion of tissue growth and development, stimulation of cell proliferation, effects on lipid and carbohydrate metabolism, anti-aging, anti-inflammatory, anabolic, anti-oxidant, neuro- and hepatoprotective properties. Our knowledge about the GH/IGF axis is diverse, partly contradictory, their research is continued intensively nowadays. We considered it worthwhile to review and interpret this information. Study on GH/IGF medical reports, with particular reference to the less known metabolic control. 75% of the growth factors are produced in the liver by GH and insulin stimulation; their effects are expressed on specific receptors, and modified by specific binding proteins. IGF1 directly increases the muscle mass, bone density, and the structure of the bones. Intestinal microbiota induces secretion of IGF1, which promotes the development and remodeling of the bones. Short-chain fatty acids, produced in microbial fermented fibers, induce secretion of IGF1, suggesting that microbial activity also affects bone health via IGF1. IGF1 also has a direct and indirect glucose-lowering effect, enhances free fatty acid oxidation in the muscle, reducing the flow of free fatty acid into the liver, improving insulin signaling, resulting in the reduction of hepatic glucose output, and improves insulin sensitivity. IGF1 directly influences the expression of circadian BMAL1 in hypothalamic cells: this refers to the newly recognized 'zeitgeber' role of IGF1. The bioactivity of insulin-like peptides in the brain is characterized by neuronal survival, excitatory and inhibitory neurotransmission, maintenance of normal free fatty acid levels, improvement of cognitive function, protection against cell damage, neurogenesis and angiogenesis. The effects of IGF2 are less outlined, however, it has a relevant role in the development of the fetus, and acts protectively on the brain. Lack or over-expression of IGF1 can be detected or may causally associated in many pathological conditions. According to these collected data, insulin sensitivity may be improved by different pathways. The role of IGFs in these processes should be a task of future research. Orv Hetil. 2019; 160(45): 1774-1783.

[The role of gut microbiota in chronic liver diseases, and treatment possibilities]

The community of microorganisms in the intestine, namely gut microbiome lives in symbiosis with the host, contributing to its homeostasis and influencing it simultaneously. It can be suspected that gut microbiome plays a central role in the pathophysiology of intestinal and extraintestinal diseases: determining their development, progress and complications. Recently, intestinal microbiome has become a highlighted field of interest and important topic in research, especially in hepatology. It is in the focus of relevant research as the liver is the organ which meets nutrients, bacterial components, toxins and metabolites at first, as a filter. The evolvement of different liver diseases - just like alcoholic and non-alcoholic fatty liver disease, steatohepatitis, cirrhosis or hepatocellular carcinoma - correlates with the changed composition and activity of gut microbiome. Thus, it can be hypothesized that pre-, pro- and antibiotics could have an impact on the treatment of these diseases. In our review article, the relationship between intestinal flora and liver diseases with different etiologies as well as therapeutic possibilities are discussed. Orv Hetil. 2018; 159(36): 1465-1474.

[Physiological patterns of intestinal microbiota. The role of dysbacteriosis in obesity, insulin resistance, diabetes and metabolic syndrome]

The intestinal microbiota is well-known for a long time, but due to newly recognized functions, clinician's attention has turned to it again in the last decade. About 100 000 billion bacteria are present in the human intestines. The composition of bacteriota living in diverse parts of the intestinal tract is variable according to age, body weight, geological site, and diet as well. Normal bacteriota defend the organism against the penetration of harmful microorganisms, and has many other functions in the gut wall integrity, innate immunity, insulin sensitivity, metabolism, and it is in cross-talk with the brain functions as well. It's a recent recognition, that intestinal microbiota has a direct effect on the brain, and the brain also influences the microbiota. This two-way gut-brain axis consists of microbiota, immune and neuroendocrine system, as well as of the autonomic and central nervous system. Emerging from fermentation of carbohydrates, short-chain fatty acids develop into the intestines, which produce butyrates, acetates and propionates, having favorable effects on different metabolic processes. Composition of the intestinal microbiota is affected by the circadian rhythm, such as in shift workers. Dysruption of circadian rhythm may influence intestinal microbiota. The imbalance between the microbiota and host organism leads to dysbacteriosis. From the membrane of Gram-negative bacteria lipopolysacharides penetrate into the blood stream, via impaired permeability of the intestinal mucosa. These processes induce metabolic endotoxaemia, inflammation, impaired glucose metabolism, insulin resistance, obesity, and contribute to the development of metabolic syndrome, type 2 diabetes, inflammarory bowel diseases, autoimmunity and carcinogenesis. Encouraging therapeutic possibility is to restore the normal microbiota either using pro- or prebiotics, fecal transplantation or bariatric surgery. Human investigations seem to prove that fecal transplant from lean healthy individuals into obese diabetic patients improved all the pathological parameters. Wide spread use of bariatric surgery altered gut microbiota and improved metabolic parameters apart from surgery itself. Pathomechanism is not yet completely clarified. Clinicians hope, that deeper understanding of complex functions of intestinal microbiota will contribute to develop more effective therapeutic proceedings against diabetes, metabolic syndrome, and obesity.