Effects of Mycobacterium vaccae ATCC 15483T on body weight, visceral adiposity, hippocampal neuroinflammation, and anxiety-like defensive behavioral responses in male and female C57BL/6N mice in a murine model of shift work
Across the world, there some occupations require traditional daytime work schedules, while other occupations require shift work, where individuals work overnight shifts. People engaged in shift work experience circadian disruption and tend to eat more high-fat, high-sugar foods due to a combination of biological, environmental, and behavioral factors. The combination of circadian disruption and consumption of a Western-style diet (WD) creates a “two-hit” metabolic challenge that increases the risk for dysregulation of the gut microbiome, systemic inflammation, metabolic syndrome, type 2 diabetes, cardiovascular disease, and stress-related psychiatric disorders for which inflammation is considered a risk factor. However, novel interventions are being tested in hopes to find a promising therapy against this “two-hit” metabolic challenge. In this study we set out to determine if immunization of male and female C57BL/6N mice with M. vaccae ATCC 15483T, a bacterium with anti-inflammatory, immunoregulatory, and stress resilience properties, protects against weight gain, visceral adipose tissue accumulation, neuroinflammation, cognitive impairment, and anxiety-like defensive behavioral responses induced by chronic disruption of rhythms (CDR) and consumption of a WD. Mice received a subcutaneous injection of 0.1 mg/0.1 ml of a whole-cell, heat-killed preparation of M. vaccae ATCC 15483T or 0.1 ml of sterile borate-buffered saline (BBS) vehicle once a week for 11 weeks starting on Experimental Day -21. On Experimental Day 0, mice were assigned to either an eight-week CDR condition or normal light:dark (NLD) conditions and either a continuous control diet or WD for ten weeks starting on Experimental Day 0. Mice were tested for cognitive function in the object location memory test on Experimental Days 53-54, and for anxiety-like defensive behavioral responses in the open-field test and elevated plus-maze on Experimental Days 55-56 and 57-58, respectively. Fecal samples were collected on Experimental Days -22, -1, 48, and 62-63 to evaluate the diversity and community composition of the gut microbiome. Following euthanasia, we collected visceral adipose tissue to assess visceral adipose tissue accumulation and hippocampus for analysis of biomarkers of neuroinflammation using real-time reverse transcription-polymerase chain reaction. Consumption of a WD altered the diversity and community composition of the gut microbiome, notably increasing the Firmicutes:Bacteroidota ratio. Male mice, but not female mice, responded to the WD with increased body weight gain and increased visceral adiposity within the eight-week protocol. Among male mice, immunization with M. vaccae ATCC 15483T attenuated body weight gain and prevented WD-induced increases in visceral adipose tissue accumulation. Immunization with M. vaccae ATCC 15483T decreased hippocampal Nlrp3 mRNA expression, a biomarker of microglial priming, in male mice but not female mice. Finally, immunization with M. vaccae ATCC 15483T decreased anxiety-like defensive behavioral responses in the open-field test in male and female mice, specifically in the WD/CDR condition. These data suggest that M. vaccae ATCC 15483T can protect against negative outcomes of WD even when coupled with CDR in a murine model of shift work.
Across the world, there some occupations require traditional daytime work schedules, while other occupations require shift work, where individuals work overnight shifts. People engaged in shift work experience circadian disruption and tend to eat more high-fat, high-sugar foods due to a combination of biological, environmental, and behavioral factors. The combination of circadian disruption and consumption of a Western-style diet (WD) creates a “two-hit” metabolic challenge that increases the risk for dysregulation of the gut microbiome, systemic inflammation, metabolic syndrome, type 2 diabetes, cardiovascular disease, and stress-related psychiatric disorders for which inflammation is considered a risk factor. However, novel interventions are being tested in hopes to find a promising therapy against this “two-hit” metabolic challenge. In this study we set out to determine if immunization of male and female C57BL/6N mice with M. vaccae ATCC 15483T, a bacterium with anti-inflammatory, immunoregulatory, and stress resilience properties, protects against weight gain, visceral adipose tissue accumulation, neuroinflammation, cognitive impairment, and anxiety-like defensive behavioral responses induced by chronic disruption of rhythms (CDR) and consumption of a WD. Mice received a subcutaneous injection of 0.1 mg/0.1 ml of a whole-cell, heat-killed preparation of M. vaccae ATCC 15483T or 0.1 ml of sterile borate-buffered saline (BBS) vehicle once a week for 11 weeks starting on Experimental Day -21. On Experimental Day 0, mice were assigned to either an eight-week CDR condition or normal light:dark (NLD) conditions and either a continuous control diet or WD for ten weeks starting on Experimental Day 0. Mice were tested for cognitive function in the object location memory test on Experimental Days 53-54, and for anxiety-like defensive behavioral responses in the open-field test and elevated plus-maze on Experimental Days 55-56 and 57-58, respectively. Fecal samples were collected on Experimental Days -22, -1, 48, and 62-63 to evaluate the diversity and community composition of the gut microbiome. Following euthanasia, we collected visceral adipose tissue to assess visceral adipose tissue accumulation and hippocampus for analysis of biomarkers of neuroinflammation using real-time reverse transcription-polymerase chain reaction. Consumption of a WD altered the diversity and community composition of the gut microbiome, notably increasing the Firmicutes:Bacteroidota ratio. Male mice, but not female mice, responded to the WD with increased body weight gain and increased visceral adiposity within the eight-week protocol. Among male mice, immunization with M. vaccae ATCC 15483T attenuated body weight gain and prevented WD-induced increases in visceral adipose tissue accumulation. Immunization with M. vaccae ATCC 15483T decreased hippocampal Nlrp3 mRNA expression, a biomarker of microglial priming, in male mice but not female mice. Finally, immunization with M. vaccae ATCC 15483T decreased anxiety-like defensive behavioral responses in the open-field test in male and female mice, specifically in the WD/CDR condition. These data suggest that M. vaccae ATCC 15483T can protect against negative outcomes of WD even when coupled with CDR in a murine model of shift work.
University of California San Diego Microbiome Initiative