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Increased consumption of added sucrose and high-fructose corn syrup in the human diet has been associated with increasing incidence of obesity and metabolic disease. There are currently no reliable, objective biomarkers for added sugar intake that could be used in individuals or population settings. 13C is a stable isotope of carbon, and measurement of blood 13C content has been proposed as a marker of added sugar consumption. This study aimed to determine if breath 13CO2 could represent an alternative, noninvasive biomarker to monitor added sugar intake. We undertook retrospective analyses of eight preclinical and human 13C-breath studies to define baseline breath 13CO2 characteristics. All samples were analyzed using isotope ratio mass spectrometry, and breath 13CO2 was expressed as the delta value, δ expressed as parts per thousand (‰). All data are expressed as mean ± SEM, with statistical significance considered at P < 0.05. Breath δ13CO2 was significantly elevated in a cumulative manner in rats and mice that consumed a diet containing at least 15% sucrose. Mice fed an American rodent chow diet containing 50% sucrose and 15% corn starch had a significantly higher breath δ13CO2 compared with rodents consuming an Australian rodent chow diet. Furthermore, breath δ13CO2 was significantly increased in a dose-dependent manner in humans that ingested a bolus dose of sucrose. These findings suggest application for baseline breath δ13CO2 as a noninvasive biomarker for added sugar consumption, with broad application for longitudinal assessment of population sugar intake and obesity management strategies. NEW & NOTEWORTHY We have found that breath 13CO2 is increased in rats and mice consuming diets high in sucrose. We also found that human breath 13CO2 is increased in humans consuming increasing amounts of sucrose. Our collective findings suggest that breath 13CO2 represents a potential marker of added dietary sugar consumption. [ABSTRACT FROM AUTHOR]

The importance of the dipeptidyl peptidase 4 (DPP4) gene family in regulating critical biochemical pathways continues to emerge. The two most well-studied members of the family, DPP4 and fibroblast activation protein (FAP), have been investigated both as therapeutic targets for disease and as diagnostic biomarkers. The interest in DPP4 and FAP as potential disease biomarkers has been driven primarily by observations of altered expression profiles in inflammatory diseases and cancer. Furthermore, the stability and persistence of soluble DPP4 and FAP in the serum make them attractive candidate serology markers. This review summarises investigations into DPP4 and FAP as biomarkers of autoimmune disease, gut inflammation, psychosomatic disorders and malignancy and discusses their potential likelihood as clinically useful tools. [ABSTRACT FROM AUTHOR]

Chronic isoleucine supplementation prevents diet-induced weight gain in rodents. Acute-isoleucine administration improves glucose tolerance in rodents and reduces postprandial glucose levels in humans. However, the effect of chronic-isoleucine supplementation on body weight and glucose tolerance in obesity is unknown. This study aimed to investigate the impact of chronic isoleucine on body weight gain and glucose tolerance in lean and high-fat-diet (HFD) induced-obese mice. Male C57BL/6-mice, fed a standard-laboratory-diet (SLD) or HFD for 12 weeks, were randomly allocated to: (1) Control: Drinking water; (2) Acute: Drinking water with a gavage of isoleucine (300 mg/kg) prior to the oral-glucose-tolerance-test (OGTT) or gastric-emptying-breath-test (GEBT); (3) Chronic: Drinking water with 1.5% isoleucine, for a further six weeks. At 16 weeks, an OGTT and GEBT was performed and at 17 weeks metabolic monitoring. In SLD- and HFD-mice, there was no difference in body weight, fat mass, and plasma lipid profiles between isoleucine treatment groups. Acute-isoleucine did not improve glucose tolerance in SLD- or HFD-mice. Chronic-isoleucine impaired glucose tolerance in SLD-mice. There was no difference in gastric emptying between any groups. Chronic-isoleucine did not alter energy intake, energy expenditure, or respiratory quotient in SLD- or HFD-mice. In conclusion, chronic isoleucine supplementation may not be an effective treatment for obesity or glucose intolerance. [ABSTRACT FROM AUTHOR]

Dipeptidyl peptidase-4 inhibitors (DPP4i) are a class of orally available, small molecule inhibitors for the management of Type-II diabetes. A rapid, real-time, functional breath test for DPP4 enzyme activity could help to define DPP4i efficacy in patients that are refractory to treatment. We aimed to develop a selective, non-invasive, stable-isotope 13C-breath test for DPP4. In vitro experiments were performed using high (Caco-2) and low (HeLa) DPP4 expressing cells. DPP gene expression was determined in cell lines by qRT-PCR. A DPP4 selective 13C-tripeptide was added to cells in the presence and absence of the DPP4 inhibitor Sitagliptin. Gas samples were collected from the cell headspace and 13CO2 content quantified by isotope ratio mass spectrometry (IRMS). DPP4 was highly expressed in Caco-2 cells compared to HeLa cells and using the 13C-tripeptide, we detected a high 13CO2 signal from Caco2 cells. Addition of Sitaglitpin to Caco2 cells significantly inhibited this 13CO2 signal. 13C-assay DPP4 activity correlated positively with the enzyme activity detected using a colorimetric substrate. We have developed a selective, non-invasive, 13C-assay for DPP4 that could have broad translational applications in diabetes and gastrointestinal disease. [ABSTRACT FROM AUTHOR]

Increased consumption of added sucrose and high-fructose corn syrup in the human diet has been associated with increasing incidence of obesity and metabolic disease. There are currently no reliable, objective biomarkers for added sugar intake that could be used in individuals or population settings. 13 C is a stable isotope of carbon, and measurement of blood 13 C content has been proposed as a marker of added sugar consumption. This study aimed to determine if breath 13 CO 2 could represent an alternative, noninvasive biomarker to monitor added sugar intake. We undertook retrospective analyses of eight preclinical and human 13 C-breath studies to define baseline breath 13 CO 2 characteristics. All samples were analyzed using isotope ratio mass spectrometry, and breath 13 CO 2 was expressed as the delta value, δ expressed as parts per thousand (‰). All data are expressed as mean ± SEM, with statistical significance considered at P < 0.05. Breath δ 13 CO 2 was significantly elevated in a cumulative manner in rats and mice that consumed a diet containing at least 15% sucrose. Mice fed an American rodent chow diet containing 50% sucrose and 15% corn starch had a significantly higher breath δ 13 CO 2 compared with rodents consuming an Australian rodent chow diet. Furthermore, breath δ 13 CO 2 was significantly increased in a dose-dependent manner in humans that ingested a bolus dose of sucrose. These findings suggest application for baseline breath δ 13 CO 2 as a noninvasive biomarker for added sugar consumption, with broad application for longitudinal assessment of population sugar intake and obesity management strategies. NEW & NOTEWORTHY We have found that breath 13 CO 2 is increased in rats and mice consuming diets high in sucrose. We also found that human breath 13 CO 2 is increased in humans consuming increasing amounts of sucrose. Our collective findings suggest that breath 13 CO 2 represents a potential marker of added dietary sugar consumption.