Investigating the influence of the gut microbiome on diabetic renal disease

Abstract

BackgroundGut microbiota have been implicated in a large array of pathophysiological processes including obesity and diabetes. In this study, we utilized a diabetic renal disease model with or without oral antibiotic treatment to investigate how gut microbiota alter diabetic renal disease.MethodsGut microbiota biomass was depleted using a modified antibiotic treatment protocol with a mixture of 1g/L ampicillin, 1g/L neomycin, and 0.5 g/L vancomycin (modified from Rakoff‐Nahoum et al. 2004). C57BL/6J male and female mice (6‐week‐old) were randomly assigned to four different groups (n=8 per sex per group): control diet (CD), high‐fat diet (HFD), CD + antibiotics, HFD + antibiotics. The mice were treated with different diets and/or with antibiotics in drinking water for nine weeks. We measured body weight (BW), non‐fasting glucose, insulin, and glomerular filtration rate (GFR). In addition, we performed a glucose tolerance test (GTT), insulin tolerance test (ITT), and blood analysis. Finally, we did H&E staining of the kidney, and analyzed urine Na+.Results1) BW was significantly increased by HFD (vs CD) in both males and females regardless of antibiotic treatment. 2) Non‐fasting glucose showed no difference among these four groups in males and females. 3) Fasting glucose was dramatically elevated by HFD in males but not females (vs CD). For the GTT, both the peak glucose level and area under curve (AUC) were significantly increased in HFD vs CD, regardless of antibiotic treatment or sex. 4) For the ITT, HFD promoted insulin resistance as measured by changes in the AUC in both males and females. For males on a CD, antibiotics improved insulin responsiveness. 5) GFR was increased by HFD vs CD in both males and females, consistent with a HFD‐induced hyperfiltration, as we published previously with this same model (Halperin Kuhns, AJP Renal 2018). Intriguingly, GFR in females was also enhanced by antibiotic treatment on both the CD and HFD (week 9: CD, F: 182±12.7; HFD, F: 290±19.9, p<0.0001; CD + antibiotics, F: 282±12.6; HFD + antibiotics, F: 373±20.1; p=0.0005 CD vs. CD+antibiotics; p=0.01 HF vs. HF+antibiotics). Similarly, GFR in males also increased with antibiotic treatment in CD, but, not HFD (week 9: CD, M: 191±10.0; HFD, M: 385±19.3, p<0.0001; CD + antibiotics, M: 263±10.5; HFD + antibiotics, M: 390±32.7; p=0.04 CD vs. CD+antibiotics; p>0.99 HF vs. HF+antibiotics). Preliminary data using germ‐free (GF) mice, which do not have microbiota, show that GFR was also increased in GF males and females (vs. conventional mice with gut microbes).ConclusionIn this study, depletion of the gut microbiota via antibiotics increased GFR in both males and females on CD. Interestingly, on a HFD, GFR increased with antibiotics in females but not males. These data suggest that gut microbial signals may directly influence renal function; we are now working to confirm these findings and to explore the underlying mechanisms.