The paper aimed to examine the effects of probiotics on eight factors in the prediabetic population.
These were namely, fasting blood glucose (FBG), glycated haemoglobin A1c (HbA1c), homeostatic model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C).
Beneficial outcomes of probiotic supplementation on HbA1c, QUICKI, TC, TG and LDL-C were confirmed.
The paper analysed seven studies involving a total of 460 people in randomised controlled trials. The participants had impaired fasting glucose or impaired glucose tolerance or both, and were free of other major medical conditions.
Three studies used capsule probiotics while others administered probiotics milk, yogurt, powder and sachets. Apart from three studies that used only one probiotic, participants in the rest of the studies were given a combination of three or more strains.
Globally, the prevalence of prediabetes is increasing every year and at a much higher rate than that of type 2 diabetes. According to statistics, 70% of patients with prediabetes eventually develop diabetes. However, the condition is reversible.
“Probiotics exert beneficial effects on the body by regulating the intestinal microbiota. In some studies, probiotics have been shown to improve insulin resistance, regulate blood glucose homeostasis, lower blood lipids, and delay or inhibit the onset of diabetes and its complications,” said the authors.
In the paper, probiotics were observed to play an active role in blood glucose homeostasis through various mechanisms of action.
Probiotics increase the secretion of glucagon-like peptide 1 (GLP-1), an intestinal hormone critical for stimulating insulin secretion, and enable the proliferation and regeneration of pancreatic beta cells that synthetise, store and release insulin.
It was found that Lactobacillus and Bifidobacterium can indirectly increase GLP-1 production.
Specifically, pancreatic beta cell function was enhanced when Shirota-fermented milk containing the Lactobacillus casei strain was administered to prediabetic patients.
This strain was also shown to markedly reduce TC and LDL-C levels, indicating its ability to regulate lipid metabolism through cholesterol-lowering mechanisms.
Chronic low-grade inflammation is a significant pathological change in the development of diabetes. Multiple studies reported that some probiotics, such as Lactobacillus plantarum, not only decrease the levels of lipopolysaccharide (LPS) and pro-inflammatory cytokines, but also reduce harmful bacterial flora related to insulin resistance and the inflammatory response.
In patients with abnormal glucose tolerance, the proportion of ‘good bacteria’ Lactobacillus and Eubacterium eligens in the intestine increased after using oral probiotics.
In addition, certain probiotics were found to reshape the intestinal flora composition to improve digestion and absorption of nutrients. Specially, Clostridium butyricum CGMCC0313.1 was able to reduce the Firmicutes/Bacteroidetes (F/B) ratio, to regulate blood glucose homeostasis and prevent the progression of type 2 diabetes.
Several other mechanisms, such as strengthening the mucus barrier, relieving oxidative stress, increasing leptin levels and maintaining mitochondrial health, were also reported.
Defining the role of probiotics
Although the paper offers valuable references for future research and clinical translation, there are a few key limitations. These include the confined number of studies analysed, the varying types, amounts and dosage forms of probiotics administered, the lack of statistical analysis on daily diet and exercise, and the limited data on the minimum effective dose of known beneficial probiotic strains.
More large-scale, strictly controlled long-term clinical trials are needed to explore other beneficial probiotic strains, as well as provide more reliable data on the efficacy and safety of probiotics. Experiments to evaluate probiotic mechanisms of action at the molecular level should also be conducted.
“The observation period of glucolipid metabolism in prediabetic patients after discontinuation of probiotics should be prolonged to determine the extent of its efficacy,” the authors added.
Source: PubMed Central
“The effects of probiotic administration on patients with prediabetes: a meta-analysis and systematic review”
Authors: Ya Li, et al