Abstract: Provided herein are methods for determining a metabolic rate for at least one endogenous short-chain fatty acid in a subject, for diagnosing a pulmonary disease in a subject and for diagnosing a neurological disorder in a subject. Generally in the methods stable isotope labeled short-chain fatty acid are pulsed and metabolic rates are calculated in a first baseline blood sample and in a series of second blood samples obtained at intervals. The metabolic rates provide information about fatty acid metabolism and production.

Abstract: A method of predicting a composition of a meal includes obtaining data relating to concentration of a biomarker of an individual that consumed the meal, analyzing the data to determine the composition of the meal, wherein the analyzing comprises using a computational model. The computational model relies upon statistical learning techniques to breakdown meal composition into macronutrient levels.

Abstract: Provided herein are methods for diagnosing impaired nutrient absorption or determining a nutrient absorption level in an individual. A first stable absorption isotopologue of a nutrient and a second stable absorption isotopolog of the same nutrient are administered orally and intravenously, respectively, to the individual. Amounts of the first and second isotopologs are both measured in blood samples drawn periodically and a ratio of the first isotopolog to the second isotopolog is calculated providing a level of nutrient absorption. The results are compared with a healthy control or an ideal value of 1.0. The ratio less than that of a healthy control or significantly lower than 1.0 indicates an impaired nutrient absorption in the individual.

Abstract: The present invention provides methods for continuous measurement of triglyceride digestibility during a meal. A stable isotope labeled triglyceride and a free fatty acid tracer are added to the meal. The ratio between a ratio of isotope labeled fatty acid produced after digestion to free fatty acid tracer represents the percentage of digestion of triglycerides by lipase from the pancreas.

Abstract: Provided herein are methods for diagnosing impaired nutrient absorption or determining a nutrient absorption level in an individual. A first stable absorption isotopologue of a nutrient and a second stable absorption isotopologue of the same nutrient are administered orally and intravenously, respectively, to the individual. Amounts of the first and second isotopologues are both measured in blood samples drawn periodically and a ratio of the first isotopologue to the second isotopologue is calculated providing a level of nutrient absorption. The results are compared with a healthy control or an ideal value of 1.0. The ratio less than that of a healthy control or significantly lower than 1.0 indicates an impaired nutrient absorption in the individual.

Abstract: Provided herein are methods of metabolic kinetic phenotyping based on amino acids, proteins and other metabolites thereof. In the method a solution comprising a plurality of stable isotopes of amino acids is administered to the individual and one or more kinetic parameters of amino acids and the metabolites are calculated in blood samples taken periodically from the individual. The metabolic phenotype is composed from the kinetic parameters. Also provided are methods and kits for identifying a disease, such as chronic heart failure, in a patient using the metabolic parameters.

Abstract: The present invention provides methods for continuous measurement of triglyceride digestibility during a meal. A stable isotope labeled triglyceride and a free fatty acid tracer are added to the meal. The ratio between a ratio of isotope labeled fatty acid produced after digestion to free fatty acid tracer represents the percentage of digestion of triglycerides by lipase from the pancreas.

Abstract: The present invention provides methods for continuous measurement of protein and/or triglyceride digestibility during a meal. Stable isotope of 15N-spirulina protein and 2H5-phenylalanine was added to the nutritional supplement. Protein digestibility is calculated by measuring the ratio [15N]PHE to [2H5]PHE in plasma and the nutrition. In another embodiment, [1,1,1-13C3]tripalmitin and [2,2-2H2]palmitic acid were added to the meal. The ratio between [1-13C]palmitic acid/[2,2-2H2]palmitic acid will represent the percentage digestion of triglycerides by lipase from the pancreas.

Abstract: The present invention provides methods for continuous measurement of protein and/or triglyceride digestibility during a meal. Stable isotope of 15N-spirulina protein and 2H5-phenylalanine was added to the nutritional supplement. Protein digestibility is calculated by measuring the ratio [15N]PHE to [2H5]PHE in plasma and the nutrition. In another embodiment, [1,1,1-13C3]tripalmitin and [2,2-2H2]palmitic acid were added to the meal. The ratio between [1-13C]palmitic acid/[2,2-2H2]palmitic acid will represent the percentage digestion of triglycerides by lipase from the pancreas.