Interactions of Human Gut Microbiota With Intestinal Sweet Taste Receptors

Inclusion Criteria: 1. Able to provide written informed consent 2. Age 18-45 years 3. Weight stable (± 3 kg) during the 6 months prior to enrollment 4. BMI ≤ 25 kg/m2 5. Consumption of less than a can of diet beverage or a spoonful of NCASs weekly (or each equivalent from foods) during the past month Exclusion Criteria: 1. Known coronary artery disease, angina or congestive heart failure 2. Type 1 or Type 2 Diabetes (A1c ≥6.5%) 3. Bleeding disorders 4. Hemoglobin level \< 12.5 g/dL for women; hemoglobin level \< 13.0 g/dL for men 5. Acute or chronic infections 6. Hepatitis and/or cirrhosis 7. Severe asthma or chronic obstructive pulmonary disease 8. Renal insufficiency or nephritis (creatinine \> 1.6 mg/dl) 9. Prior bariatric surgery 10. Inflammatory bowel disease or malabsorption 11. Cancer within the last 3 years (except non-melanoma skin cancer or treated cervical carcinoma in situ) 12. Psychiatric disorders or eating disorders 13. Cushing's disease or syndrome 14. Untreated or inadequately controlled hypo- or hyperthyroidism (abnormal TSH) 15. Active rheumatoid arthritis or other inflammatory rheumatic disorder 16. Pregnant or nursing women 17. Smoking (smoking within the past 3 months) 18. Less than 4 bowel movements per week 19. Known hypersensitivity to saccharin, lactisole or any of its excipients. Excluded medications include but are not limited to: 20. Anti-diabetic agents 21. Oral, injected or chronic topical steroids (inhaled steroids for mild asthma are acceptable) 22. Antibiotic use (within the past 3 months) 23. Other drugs known to affect immune or metabolic function 24. Orlistat, phentermine, topiramate or other weight loss or anorectic agents (tricyclic antidepressants, atypical antipsychotics or other psychiatric drugs with effects on body weight)