Hypogonadism alters cecal and fecal microbiota in male mice

Abstract

Low testosterone levels increase the risk for cardiovascular disease in men and lead to shorter life spans. Our recent study showed that androgen deprivation via castration altered fecal microbiota and exacerbated risk factors for cardiovascular disease, including obesity, impaired fasting glucose, excess hepatic triglyceride accumulation, and thigh muscle weight loss only in high-fat diet (HFD)-fed male mice. However, when mice were administered antibiotics that disrupted the gut microbiota, castration did not increase cardiovascular risks or decrease the ratio of dried feces to food intake. Here, we show that changes in cecal microbiota (e.g., an increased Firmicutes/Bacteroidetes ratio and number of Lactobacillus species) were consistent with changes in feces and that there was a decreased cecal content secondary to castration in HFD mice. Castration increased rectal body temperature and plasma adiponectin, irrespective of diet. Changes in the gut microbiome may provide novel insight into hypogonadism-induced cardiovascular diseases.

Keywords: androgen receptor; cecum; gut microbiota; metabolic syndrome; non-alcoholic fatty liver disease (NAFLD); obesity; rectal body temperature; sarcopenia; stool; type 2 diabetes mellitus (T2DM).

Figures

Figure 1.

Effects of castration and diet on cecal weight and cecal microbiota. Mice were castrated or sham operated at 8-weeks-old and grown to 13 weeks with either a standard diet (SD) or high-fat diet (HFD), as described previously (A) Cecal content was weighed. (B) DNA was extracted from cecal microbiota and analyzed by real-time PCR using specific primers. Data were analyzed by Student's t-test using JMP statistical software version 8.0.1 (SAS Institute, Cary, NC, USA). Data were expressed as means ± SEM, and the threshold for a statistically significant difference between groups was set at p < 0.05 and was denoted by an asterisk (SD sham, n = 8; SD castration, n = 7; HFD sham, n = 8; HFD castration, n = 6).

Figure 2.

Effects of castration and diet on the development of fatty liver, plasma adiponectin levels, and rectal body temperature. Mice were castrated or sham operated at 8-weeks-old and grown to 24 weeks with either a standard diet (SD) or high-fat diet (HFD). (A) Rectal body temperature was measured with a digital thermometer (KN-91, Natsume Seisakusho, Tokyo, Japan) at 17 weeks of age (SD sham, n = 6; SD castration, n = 6; HFD sham, n = 7; HFD castration, n = 7). (B) The liver sections were stained with hematoxylin and eosin. Representative images of each group are shown (scale bar = 100 µm). (C) Plasma adiponectin levels were determined by western-blotting using anti-adiponectin rabbit polyclonal antibody (GTX23455, GeneTex, San Antonio, TX, USA), and the immunoreactive bands were developed as described previously. The band intensity was quantified using Image J software (ver. 1.48, National Institutes of Health, Bethesda, MD, USA) (SD sham, n = 5; SD castration, n = 5; HFD sham, n = 7; HFD castration, n = 7). Data were analyzed by Student's t-test using JMP statistical software version 8.0.1. Data were expressed means ± SEM, and the threshold for a statistically significant difference between groups was set at p < 0.05 and was denoted by an asterisk.

Figure 3.

Schematic presentation of the effects of interactive effects between castration and high-fat diet intake in male mice. Castration influenced the gut microbiota and caused obesity, hepatic steatosis, thigh muscle loss, and impaired fasting glucose in male mice in the high-fat diet (HFD)-dependent manner. These observations were not induced by castration when antibiotics were provided.