Previous studies have shown probiotic or synbiotic supplements to be advantageous during pregnancy, as they may reduce insulin resistance and enhance lipid metabolism.
However, probiotic and synbiotic's impact on GDM is debatable as while some randomised controlled trials (RCTs) reported a notable improvement in blood glucose control, others found no difference after intervention.
To better understand how probiotic/synbiotic treatment affects glucose and lipid metabolism in GDM, this meta-analysis assessed the findings from 11 randomised controlled clinical trials (RCT) involving data from 779 participants.
The authors, from the Beijing Sport University, China, conclude: “Probiotic/synbiotic could improve glucose and lipid metabolism in pregnant women with GDM. The use of specific probiotic supplementations containing Lactobacillus acidophilus and Bifidobacterium bifidum may be a promising prevention and therapeutic strategy for GDM, as they could directly act on the intestinal mucosal barrier and restore the gut flora balance.
“However, due to the heterogeneity among existing studies, further studies are warranted to address the limitations of existing evidence and better inform the management of GDM.”
GDM is the name for glucose intolerance that is discovered for the first time during pregnancy, and it affects 12.8% of pregnancies worldwide. It is a common condition that affects the mother's and the unborn child's long-term health.
Women with GDM also have a higher risk of developing type 2 diabetes, pancreatic cancer, and cardiovascular disease after giving birth, in addition to a higher risk of needing a caesarean section, shoulder dystocia, eclampsia, and other pregnancy complications.
Because either metformin or insulin therapy is frequently required to achieve optimal glycemic control, it forms the basis of GDM management. Because gut dysbiosis is a hallmark of GDM pregnancies, altering the gut microbiota through diet may offer a novel management strategy. Probiotics are a relatively new intervention that can alter the mother's and the child's glucose and lipid metabolisms as well as lower the mother's blood sugar levels.
The new meta-analysis used electronic databases Cochrane Library, Web of Science, PubMed, and EBOSCO, carrying out a systematic search of the literature published between 1 January 2012 and 1 November 2022.
To be in included in the meta-analysis, study participants had to be pregnant women with GDM and no other metabolic diseases, be avoidant of pro- or syn-biotic-containing foods, and of regular exercise intervention before and during pregnancy.
The analysis included 11 RCTs which included data from 779 participants. All of the included studies investigated the effect of probiotic/synbiotic supplements on fasting plasma glucose (FPG) in GDM.
Eight RCTs used probiotics, including Lactobacillus acidophilus, L. fermentum, L.casei, L. reuteri, L. salivarius, L. delbrueckii bulgaricus, Bifidobacterium bifidum, and Streptococcus thermophilus, as the intervention method. The remaining three RCTs used synbiotics, including L. acidophilus, L. casei, L. fermentum, L. gasseria, L. plantarum, Bififidobacterium bififidum, B.longum, B. infantis. Most of them took one capsule a day, only one study adopted two capsules a day. The daily consumption of probiotics/synbiotics varied from 1 × 109 CFU/capsule to 112.5 × 109 CFU/capsule.
The meta-analysis concluded that, compared with the placebo, probiotics/synbiotics were associated with a statistically significant improvement in FPG, fasting serum insulin (FSI), and the homoeostatic model assessment for insulin resistance (HOMA-IR), while other factors had no significant difference.
Mechanism of Action
Insulin resistance and β-cell impairment are the usual causes of GDM, so the quantity of insulin must be increased appropriately to maintain the normal metabolism of glucose. When combined with decreased insulin sensitivity, the lack of insulin secretion by β-cell during gestational diabetes leads to hyperglycemia.
Reduced adipocyte differentiation and increased adipocyte size are also associated with GDM. This modification, combined with insulin resistance, can cause lipid buildup in the liver and skeletal muscle which aggravates GDM.
High body fat levels and intake can change the normal gut microbial composition in GDM patients. Studies suggest that this could increase bacteria Firmicutes and Faecalibacterium that produce butyrate, and result in over-expression of short-chain fatty acids (SCFAs). Excess SCFAs increase lipid storage in skeletal muscle and liver, and incite glucose and lipid metabolism disorders development.
Previous studies have shown that probiotics may play a role in the intestinal mucosal barrier, improving glucose tolerance and reversing the imbalance in gut flora brought on by GDM, as SCFA levels are also regulated by probiotics. Thus, transit time of food in the intestine could slow and insulin sensitivity could increase.
In this new meta-analysis, some RCTs reported lipid profiles, and after intervention, total cholesterol (TC) showed a significant decrease. However, other clinical studies offered conflicting results, with taking probiotics or placebo in the first trimester of pregnancy having no effect on the lipid levels in the third trimester.
The authors of the study state: “We hypothesised that a duration of intervention longer than 8 weeks may have generated outcomes with larger effect sizes.”
The study did have some limitations. The numbers of participants in the included RCTs were relatively small, ranging from 20 to 60, and there was no assessment of the effect of probiotics or synbiotic supplementation on infants or the long-term effect for mothers. Additionally, the types and durations of probiotics or synbiotics were not consistent in the different studies that were included in this analysis.
The authors also state: “Eight RCTs were conducted in Iran, which means the research may show publication bias and the conclusions may not be applicable to populations from other racial backgrounds and countries.”
“The Effects of Probiotics/Synbiotics on Glucose and Lipid Metabolism in Women with Gestational Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials”
Authors: Jinhao Mu, Xian Guo, Yanbing Zhou, and Guoxia Cao.