Diabetes in cats and microbial diversity in the gut

07 Mai Diabetes in cats and microbial diversity in the gut

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Information on the possible or actual role of the gastrointestinal microbiome in the development and following consequences of a wide range of diseases and syndromes in humans and animals appears almost daily in the scientific and everyday media. Diabetes mellitus type 2 („adult onset“) in humans is an often mentioned disease. There is increasing evidence that gastrointestinal dysbiosis is present in people suffering from it. In particular, the number of bacteria that produce butyrate, a short-chain fatty acid (SCFA), has decreased in human type 2 diabetes patients compared to controls. The short-chain fatty acids acetate, butyrate and propionate are produced by the fermentation of complex polysaccharides by microbes in the colon; these substances help to facilitate glucose and energy metabolism and support local immune function. Butyrate in particular provides energy for the cells of the colon mucosa and can increase insulin sensitivity and energy expenditure. A reduced butyrate level can be significantly associated with the development of insulin resistance.

The feline diabetes mellitus

The feline diabetes mellitus (FDM) is considered to be an animal model of human type 2 diabetes and, like its human counterparts, cats with this disease are middle to old age, often overweight to obese, and have impaired insulin secretion, peripheral insulin resistance, loss of beta-islet cells and the development of amyloid deposits in the insulin-producing pancreatic islets.

A recent study on feline diabetes mellitus

The current study involved the genetic sequencing of 121 microbial DNA samples from the faeces of 82 private cats from Denmark and Switzerland and consisted of two parts:

  1. a cross-sectional study to identify differences between the gastrointestinal microbiomes of diabetic, healthy lean (Body Condition Score 4-5 of 9) and healthy overweight/obese cats (Body Condition Score 7-9 of 9), and
  2. an intervention study to determine if changes in the gastrointestinal microbiome of a subgroup of these cats can be detected by feeding a high protein/low carbohydrate commercial diet specifically designed for diabetic cats.

After extraction from the faeces samples, microbial DNA concentrations were estimated and then amplified by PCR. The composition of the fecal bacterial microbiota was determined by next-generation sequencing of 16S ribosomal RNA.

The cats in the study

Of the 121 faeces samples, the samples from 62 cats (23 with diabetes, 15 overweight and 24 normal weight) had sufficient nucleic acid levels to be included in a statistical analysis. Most of the cats were only indoors, and few had limited access to the outside. All cats in the study were over 6 years old, had not received antibiotics in the four months prior to the start of the study, and had not received probiotics or prebiotics within two weeks of admission.

Diabetes cats have a less diverse microbiome

All but one (newly diagnosed) cat with diabetes received insulin, different preparations were used. In the genetic sequencing part of the study it was found that the diabetic cats had a less diverse gastrointestinal microbiome than the other two groups. There were also differences in the blood counts:

  • hemoglobin and pack volume cells correlated positively with the richness of the gastrointestinal microbiome
  • serum bile acid, serum fructosamine and serum glucose levels were negatively correlated with the richness of the gastrointestinal microbiome
  • Compared to the healthy cats, the diabetic cats had lower levels of Bacteroidetes, Bacteroida, Bacteroidales, Prevotellaceae and Prevotella. By the way, breed, sex and age of the examined animals had no influence on the composition of the microbial intestinal flora.

The reduced diversity of the gastrointestinal microbiome and the tendency to harbour more pro-inflammatory microbes, as well as the significant decrease in butyrate-producing bacteria observed in diabetic cats were parallel to the findings in people with type 2 diabetes. These changes were not found in the healthy group of overweight cats, so it is likely that body expression alone is not predisposed to the development of feline diabetes.

No improvement of the microbiome through feed conversion

In the second, interventional part of the study, only a subgroup of the cats from Denmark (10 cats with diabetes mellitus, 11 normal weight and 13 overweight) were fed a commercial dry food rich in protein and low in carbohydrates (Royal Canin Diabetic Feline) for four weeks, and faecal samples were again collected for analysis of the microbial genetic material. The dietary intervention did not improve the diversity or composition of the gastrointestinal microbiome in the diabetic cats compared to the other two groups. Although the small sample size and relatively short treatment duration in this part of the study may have contributed to the absence of the observed significant change, it is possible that probiotic supplementation, including butyrate-producing bacteria, or faecal transplantation may be important in the future treatment of diabetic cats. Another potential avenue for future research could be to investigate the effect of a high-protein canned diet designed for diabetic cats on the gastrointestinal microbiome of these patients and on healthy controls.

Source: Kieler IN, Osto, M, et al. Diabetic cats have decreased gut microbial diversity and a lack of butyrate producing bacteria. Sci Rep 2019;9:4822.

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