In a recent study published in the journal Nutrients, researchers conducted a systematic review of human clinical trials that examined the administration of oral probiotics to improve gut microflora and manage type 2 diabetes mellitus.

Study: The Effects of Oral Probiotics on Type 2 Diabetes Mellitus (T2DM): A Clinical Trial Systematic Literature Review. Image Credit: FOTOGRIN / Shutterstock

Background

Type 2 diabetes mellitus is rapidly becoming a major global health concern. It is a metabolic disorder where the body either does not respond to insulin or does not produce enough insulin. The insufficient insulin response results in an increase in blood glucose levels, and the prolonged hyperglycemia eventually affects other organ systems, including the circulatory and nervous systems. The development and progression of type 2 diabetes mellitus is attributed to a combination of metabolic, genetic, and environmental factors. However, despite the genetic predisposition to developing type 2 diabetes mellitus, various modifiable risk factors such as dietary and lifestyle habits can help in the management of the disease.

Growing evidence indicates that the gut microbiome plays a significant role in health and diseases, and dysbiosis in the gut microbiome is linked to the progression of a wide range of diseases affecting multiple organ systems. Gut microbiome dysbiosis is also implicated in the etiology of type 2 diabetes mellitus, with the imbalance in the gut microflora abundance and diversity having an impact on the glycemic regulation of the host. The use of prebiotics and probiotics to modulate the gut microbiome has also been extensively investigated in the context of disease management.

About the study

In the present study, the researchers examined clinical trials that have investigated the effectiveness of oral probiotics in the management of type 2 diabetes mellitus and discussed the species composition of probiotics, as well as interventions involving combinations of probiotics.

The gut microbiome is involved in critical physiological processes such as immunity and nutrient absorption. Furthermore, studies in non-human mammalian models have clearly shown that metabolic disorders and the gut microbiome are strongly interlinked. However, the evidence for this association from human studies remains contentious. Therefore, only completed human clinical trials were included in the review, and those conducted on animal models and reviews and meta-analyses were excluded.

The studies included in the review addressed multiple aspects of type 2 diabetes mellitus, such as lipid profiles, glycemic metabolism, cardiovascular factors, fecal analysis, and inflammation. Only those studies having participants with confirmed type 2 diabetes mellitus were included in the study, and those involving prediabetic patients or conducting comorbidity analyses were excluded. Additionally, studies involving non-oral probiotics or with study participants below the age of 18 were also excluded.

Study characteristics such as the type of clinical trial, age of the study population, and number of participants were collected. Additionally, characteristics of the probiotic intervention, such as the average colony forming units administered per day, the duration of the administration, the number of administrations per day, the probiotic composition, the number of strains in the probiotics, genus level identification of the microbe species in the probiotic, and the placebos used in the study were also obtained from the studies.

The examined outcomes included parameters associated with glycemic and lipid levels, kidney and cardiovascular indicators, anthropometric measurements, oxidative stress and other inflammation indicators, and fecal analysis.

Results

The findings showed that about 64% of the studies included in the review reported an improvement in at least one of the parameters related to the glycemic levels, while 45% of the studies reported improvements in at least one of the parameters related to lipid levels after the administration of oral probiotics. However, none of the studies indicated any uniform improvements in all parameters related to lipid and glycemic levels or blood pressure.

The authors believe that wide-ranging variations in the composition of the probiotics administered, as well as in the dosage and duration of the probiotic interventions, could explain the inconsistent findings across studies. However, the co-administration of oral probiotic interventions along with metformin treatment was found to significantly improve glycemic control in type 2 diabetes patients.

The findings about the overall effects of probiotic interventions on inflammation were inconclusive, although a few studies reported improvements in systolic blood pressure in association with probiotic interventions.

Conclusions

Overall, the findings indicated that administering probiotic interventions for improving gut microbiota in type 2 diabetes patients is not associated with any adverse reactions. In patients undergoing metformin treatment, it significantly improves glycemic control. Additional clinical trials and studies are required to understand specific factors, such as the impact of different microbial strains and optimal dosage of probiotic interventions to improve outcomes in type 2 diabetes patients.

Written by

Dr. Chinta Sidharthan

Chinta Sidharthan is a writer based in Bangalore, India. Her academic background is in evolutionary biology and genetics, and she has extensive experience in scientific research, teaching, science writing, and herpetology. Chinta holds a Ph.D. in evolutionary biology from the Indian Institute of Science and is passionate about science education, writing, animals, wildlife, and conservation. For her doctoral research, she explored the origins and diversification of blindsnakes in India, as a part of which she did extensive fieldwork in the jungles of southern India. She has received the Canadian Governor General’s bronze medal and Bangalore University gold medal for academic excellence and published her research in high-impact journals.