Background: A high-calorie diet results in the development of prediabetes (PD) or type 2 diabetes mellitus (T2DM). This diet has been reported to cause changes in microbial composition, concentration levels of glycemic parameters, and immune cells or inflammatory cytokines. This systematic review and meta-analysis aimed to evaluate the effects of prebiotics, as well as Mediterranean and plant-based dietary interventions, on gut microbiota composition and glucose homeostasis in individuals with PD or T2D. Methods: This systematic review and meta-analysis was developed according to the 2020 PRISMA guidelines and checklist. PubMed, EBSCOhost and Google Scholar were the three databases that were used to search for electronically published studies. Data extraction was conducted and examined by the reviewers and all the eligible studies were selected. To test for the quality and biases of the included studies, the Downs and Black checklist was used, followed by the use of Review Manager 5.4. A forest plot was used for meta-analysis and sensitivity analysis. The strength of the evidence was assessed using the Grading of Recommendation Assessment, Development and Evaluation approach. Results: Overall, eight studies met the inclusion criteria: seven focused on patients with T2D, and one focused on patients with PD. The prebiotic dietary intervention did not have a statistically significant effect on glycemic control, including fasting blood glucose (FBG) and glycated hemoglobin (HbA1c). However, one study investigating the Mediterranean diet reported a significant effect on glycemic control. Both prebiotic and Mediterranean dietary interventions were found to beneficially influence gut microbial composition in the intervention groups compared to the placebo groups. No studies assessed the impact of a plant-based diet on microbial composition and glucose parameters. Conclusions: This review indicated that dietary intervention with a prebiotic or Mediterranean diet shows to beneficially improve the gut microbiota composition of Firmicutes, Bacteroidetes and Bifidobacteria in patients with PD or T2D. However, their beneficial effects on FBG and HbA1c were less clear and uncertain due to limited reports, particularly regarding the Mediterranean dietary intervention.

Given the growing global threat and rising prevalence of type 2 diabetes mellitus (T2DM), addressing this metabolic disease is imperative. T2DM is preceded by prediabetes (PD), an intermediate hyperglycaemia that goes unnoticed for years in patients. Several studies have shown that gut microbial diversity and glucose homeostasis in PD or T2DM patients are affected. Therefore, this review aims to synthesize the existing literature to elucidate the association between high-calorie diets, intestinal permeability and their correlation with PD or T2DM. Moreover, it discusses the beneficial effects of different dietary interventions on improving gut health and glucose metabolism. The primary factor contributing to complications seen in PD or T2DM patients is the chronic consumption of high-calorie diets, which alters the gut microbial composition and increases the translocation of toxic substances from the intestinal lumen into the bloodstream. This causes an increase in inflammatory response that further impairs glucose regulation. Several dietary approaches or interventions have been implemented. However, only a few are currently in use and have shown promising results in improving beneficial microbiomes and glucose metabolism. Therefore, additional well-designed studies are still necessary to thoroughly investigate whether improving gut health using other types of dietary interventions can potentially manage or reverse PD, thereby preventing the onset of T2DM.

Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Prediabetes, a metabolic state characterized by elevated blood glucose levels, has been associated with various systemic complications. However, its effects on pulmonary vascular function and pulmonary fibrosis remain poorly understood. This systematic review aims to summarize existing evidence on the impact of type 2 diabetes mellitus and prediabetes on these aspects. This protocol was prepared in accordance with the PRISMA 2020 guidelines for reporting protocols. Objective: To achieve our aim, we will examine published prospective observational studies, case-control studies, cohort studies, and cross-sectional studies involving non-diabetic, type 2 diabetic, and prediabetic reports. Methods: To achieve our aim, we will examine published prospective observational studies, case-control studies, cohort studies, and cross-sectional studies involving non-diabetic, type 2 diabetic, and prediabetic reports. Our database search will encompass Google Scholar, PubMed, Embase and Web of Science. The process of data extraction and quality assessment will be carried out independently by three reviewers, with a subsequent screening of results to ensure adherence to eligibility criteria. The STROBES checklist will be applied to evaluate the risk of bias. In the meta-analysis and sensitivity analysis, we will employ the Review Manager v5.4 Forrest plot. To gauge the quality of evidence, we will utilize the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results: This protocol provides guidance for systematically exploring articles investigating pulmonary vascular function and fibrosis within diabetic and pre-diabetic states. The outcomes derived from this protocol will not only steer the direction of future research but also inform the subsequent investigative endeavors. Conclusions: It is noteworthy that this systematic review will rely on publicly accessible data, which will be collected after the release of this protocol. This protocol serves as a compass for exploring articles that delve into studies about the prediabetic state, specifically in relation to assessments of pulmonary vascular function and pulmonary fibrosis. The outcomes generated from this protocol will offer valuable guidance for future research endeavors. Clinical Trial: The protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO) with registration number “CRD42023478267”, dated 14 November 2023.

UNSTRUCTURED Prediabetes, a metabolic state characterized by elevated blood glucose levels, has been associated with various systemic complications (1). However, its effects on pulmonary vascular function and pulmonary fibrosis remain poorly understood. This systematic review aims to summarize existing evidence on the impact of type 2 diabetes mellitus and prediabetes on these aspects. This protocol was prepared in accordance with the PRISMA 2020 guidelines for reporting protocols. To achieve our aim, we will examine published prospective observational studies, case-control studies, cohort studies, and cross-sectional studies involving non-diabetic, type 2 diabetic, and prediabetic reports. Our database search will encompass Google Scholar, PubMed, Embase and Web of Science. The process of data extraction and quality assessment will be carried out independently by three reviewers, with a subsequent screening of results to ensure adherence to eligibility criteria. The STROBES checklist will be applied to evaluate the risk of bias. In the meta-analysis and sensitivity analysis, we will employ the Review Manager v5.4 Forrest plot. To gauge the quality of evidence, we will utilize the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. It is noteworthy that this systematic review will rely on publicly accessible data, which will be collected after the release of this protocol. This protocol serves as a compass for exploring articles that delve into studies about the prediabetic state, specifically in relation to assessments of pulmonary vascular function and pulmonary fibrosis. The outcomes generated from this protocol will offer valuable guidance for future research endeavours.