Lacticaseibacillus paracasei Glu-07: A Promising Probiotic Candidate for the Management of Type 2 Diabetes Mellitus

Abstract

The global prevalence of type 2 diabetes mellitus (T2DM) is currently surging, posing significant health and socioeconomic burdens. Probiotics have emerged as promising interventions due to their safety and potential metabolic benefits. Gut microbiota plays a critical role in the pathophysiology of metabolic diseases in humans, offering valuable insights for therapeutic strategies such as probiotics. Here, aiming to identify novel probiotics from the human gut microbes to combat T2DM, a total of 203 human intestinal bacterial strains were screened in vitro to evaluate their enzymatic inhibition of α-glucosidase and α-amylase, in which Lacticaseibacillus paracasei Glu-07 (= QH-142 = CGMCC 23796) exhibited the highest inhibitory efficacy (81.05% and 72.56% for α-glucosidase and α-amylase, respectively). In HepG2 cells, L. paracasei Glu-07 elevated glucose uptake and consumption by 22.4% and 85.8%. Oral administration of strain Glu-07 in diabetic mice significantly improved hyperglycemia, hyperlipidemia, and restored the structure and composition of gut microbiota toward a healthier profile. Mechanistically, strain Glu-07 activated the AMPK-AKT1-GSK3β/FOXO1 signaling pathways by modulating the expression of key genes, enhanced glycolysis and fatty acid ꞵ-oxidation, and inhibited gluconeogenesis and lipogenesis. It also stimulated GLP-1 secretion, potentially via triggering the GPR41/43-GLP-1 axis, and increased the abundance of beneficial gut microbes, such as Akkermansia muciniphila (~ threefold). The dual regulations synergistically support strain Glu-07 as a promising probiotic candidate for T2DM management.

Fig. 1

In vitro screening to assess the inhibitory effect of human gut microbes on ɑ-glucosidase and ɑ-amylase. a A schematic illustrating the in vitro screening process, including sample preparation of tested strains, execution of enzymatic inhibition assays, and data collection for assessment. b, c Table list (b) and bar graphs (c) of the top 20 strains inhibiting ɑ-glucosidase and ɑ-amylase. All strains were subjected to three rounds of screening. Data were presented as mean ± sem. vs. Control, *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 2

The glucose-lowering potentials assessments of strain Glu-07. The dosage-dependent inhibition of strain Glu-07 to a ɑ-glucosidase and b ɑ-amylase. c Cell viability assay in HepG2 cells treated with varied concentrations of strain Glu-07 culture supernatants. d Glucose uptake assay in HepG2 cells. e Glucose consumption in HepG2 cells. Insulin was used as a positive control. Data were expressed as mean ± sem, vs. Control, *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 3

Oral administration of strain Glu-07 improves hyperglycemia in STZ + HFD-induced diabetic mice. a Schematic of animal experiments in this study. b Weekly fasting blood glucose levels during the whole experimental period. c AUC measurement of fasting blood glucose level curves. d OGTT test. e AUC of OGTT curves. f Serum glucose level. g Serum insulin level. h Serum GLP-1 level. i Serum GSP level. j Blood HbA1c level. k HOMA-IR index. STZ, Streptozotocin; HFD, High-fat diet. OGTT, Oral glucose tolerance Test; GLP-1, Glucagon-like peptide-1; GSP, glycated serum protein; HbA1c, Hemoglobin A1c; HOMA-IR, Homeostatic model assessment-insulin resistance. Data were expressed as mean ± sem, vs. Model, *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 4

Treatment with strain Glu-07 alleviates hyperlipidemia and regulates key genes participating in glucose and lipid metabolism. a Body weight curves of mice. b Body weight gain. c Liver weight of mice. d Serum lipids levels. e Hepatic lipids content. f Representatives of liver HE staining. g Gene expression of AMPK, AKT1, GSK3ꞵ, and FOXO1 in liver. h The relative mRNA level of genes involving in glycolysis (GCK) and gluconeogenesis (PEPCK and G6PC) in liver. i Hepatic genes expression of GLUT2 and GLUT4. j Colonic genes expression of GLP-1R, GPR41 and GPR43. k The relative mRNA level of genes involving in lipid synthesis (PPARγ, SREBP1c, FAS, SCD1, HMGCR, and CPT1) in liver. TC, Total cholesterol; TG, Total triglycerides; LDL-c, Low-density lipoprotein cholesterol; HDL-c, High-density lipoprotein cholesterol; AMPK, AMP-activated protein kinase; AKT1, Protein kinase B; GSK3ꞵ, Glycogen synthase kinase-3β; FOXO1, Forkhead box protein O1; GCK, Glucokinase; PEPCK, Phosphoenolpyruvate carboxykinase; G6PC, Glucose-6-phosphatase; GLUT2, Glucose transporter 2; GLUT4, Glucose transporter 4; GLP-1R, Glucagon-like peptide-1 receptor; GPR41, G protein-coupled receptor 41; GPR43, G protein-coupled receptor 43; PPARγ, Peroxisome proliferator-activated receptor γ; SREBP1c, Sterol regulatory element binding protein-1c; FAS, Fatty acid synthase; SCD1, Stearoyl-CoA desaturase 1; HMGCR, 3-Hydroxy-3-methylglutaryl-CoA reductase; CPT1, Carnitine palmitoyltransferase 1. Data were expressed as mean ± sem, vs. Model, *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant

Fig. 5

Strain Glu-07 positively modulate gut microbiota in T2DM mice. a α-diversity of gut microbiota was assessed by a Chao1 and b Shannon c Simpson indices. d Principal coordinate analysis (PCoA) of gut microbiota. Profile diagrams of the gut microbiota at the e phylum, f genus, and g species levels. h The relative abundance of three representative beneficial species that were significantly increased in response to strain Glu-07. i The relative abundance of two opportunistic pathogen species that were significantly decreased in response to strain Glu-07. j Volcano plots of differential bacteria in strain Glu-07 vs. model group. k The significantly altered differential bacteria in mice. *p < 0.05, **p < 0.01, ***p < 0.001