How neutering changes gut bacteria and weight in dogs

Abstract

Neutering is a significant risk factor for obesity in dogs. Changes in gut microbiota and its metabolites have been identified as a key player during obesity progression. However, the mechanisms that promote neuter-associated weight gain are not well understood. Therefore, in this study, sixteen clinically healthy Beagle dogs (6 male and 10 female, mean age&#x2005;=&#x2005;8.22&#x2005;&#xb1;&#x2005;0.25 mo old) were neutered. Body weight (BW) and body condition score (BCS) were recorded at 1 d before neutering, 3, 6, 10, 16, and 21 mo after neutering. Dogs were grouped based on their BCS as ideal weight group (IW, n&#x2005;=&#x2005;4, mean BW&#x2005;=&#x2005;13.22&#x2005;&#xb1;&#x2005;1.30 kg, mean BCS&#x2005;=&#x2005;5.00&#x2005;&#xb1;&#x2005;0.41) and obese group (OB, n&#x2005;=&#x2005;12, mean BW&#x2005;=&#x2005;18.57&#x2005;&#xb1;&#x2005;1.08 kg, mean BCS&#x2005;=&#x2005;7.92&#x2005;&#xb1;&#x2005;0.82) at 21 mo after neutering. Serum lipid profile, glucose, and hormones and fecal microbiota and short-chain fatty acids (SCFAs) were measured. Our results showed that OB dogs had greater (P&#x2005;<&#x2005;0.0001) BW (18.57 vs. 13.22 kg), BCS (7.92 vs. 5.00), and average daily gain (12.27 vs. 5.69 g/d) than IW dogs at 21 mo after neutering, and the obesity rate was up to 60%. In addition, significant increases (P&#x2005;<&#x2005;0.05) in serum triglyceride (TG, 1.10 vs. 0.56 mmol/L) and high-density lipoprotein cholesterol (HDL-C, 6.96 vs. 5.40 mmol/L) levels and a significant decrease (P&#x2005;<&#x2005;0.05) in serum adiponectin (APN, 54.06 vs. 58.39 &#x3bc;g/L) level were observed in OB dogs; serum total cholesterol (4.83 vs. 3.75 mmol/L) (P&#x2005;=&#x2005;0.075) and leptin (LEP, 2.82 vs. 2.53 &#x3bc;g/L) (P&#x2005;=&#x2005;0.065) levels tended to be greater in OB dogs; there was a trend towards a lower (P&#x2005;=&#x2005;0.092) APN/LEP (19.32 vs. 21.81) in OB dogs. Results of fecal microbial alpha-diversity showed that Observed_species and Chao1 indices tended to be lower (P&#x2005;=&#x2005;0.069) in OB dogs. The STAMP and LEfSe analyses revealed that OB dogs had a greater (P&#x2005;<&#x2005;0.05 and LDA&#x2005;>&#x2005;2) reduction in relative abundances of Bacteroides, Prevotella_9, and Megamonas than IW dogs. In addition, OB dogs also had greater (P&#x2005;<&#x2005;0.05) reduction in fecal acetate, propionate, and butyrate concentrations than IW dogs. Moreover, clear negative correlations (|r|&#x2005;>&#x2005;0.5 and P&#x2005;<&#x2005;0.05) were found between SCFAs-producing bacteria and BW, TG, and HDL-C. The functional predictions of microbial communities based on PICRUSt2 analysis revealed that lipid metabolism and endocrine system were significantly disturbed in obese dogs after neutering. Thus, intervention with SCFAs-producing bacteria might represent a new target for the prevention or treatment of canine obesity after neutering. Moreover, weight control before neutering may also contribute to the prevention of canine obesity after neutering.