Plasma glucose kinetics and response of insulin and GIP following a cereal breakfast in female subjects: effect of starch digestibility.

BACKGROUND/OBJECTIVES: Foods with high contents of slowly digestible starch (SDS) elicit lower glycemic responses than foods with low contents of SDS but there has been debate on the underlying changes in plasma glucose kinetics, that is, respective contributions of the increase in the rates of appearance and disappearance of plasma glucose (RaT and RdT), and of the increase in the rate of appearance of exogenous glucose (RaE) and decrease in endogenous glucose production (EGP). SUBJECTS/METHODS: Sixteen young healthy females ingested in random order four types of breakfasts: an extruded cereal (0.3% SDS: Lo-SDS breakfast) or one of three biscuits (39-45% SDS: Hi-SDS breakfasts). The flour in the cereal products was labeled with (13)C, and plasma glucose kinetics were measured using [6,6-(2)H2]glucose infusion, along with the response of plasma glucose, insulin and glucose-dependent insulinotropic peptide (GIP) concentrations. RESULTS: When compared with the Lo-SDS breakfast, after the three Hi-SDS breakfasts, excursions in plasma glucose, the response of RaE, RaT and RdT, and the reduction in EGP were significantly lower (P<0.05). The amount of exogenous glucose absorbed over the 4.5-h postprandial period was also significantly lower by ~31% (P<0.001). These differences were associated with lower responses of GIP and insulin concentrations. CONCLUSIONS: Substituting extruded cereals with biscuits slows down the availability of glucose from the breakfast and its appearance in peripheral circulation, blunts the changes in plasma glucose kinetics and homeostasis, reduces excursions in plasma glucose, and possibly distributes the glucose ingested over a longer period following the meal.

Accuracy of the SenseWear Armband™ during ergocycling.

The present study aims to show the accuracy of a portable motion sensor, the SenseWear Armband, for the estimation of energy expenditure vs. energy expenditure measured by indirect calorimetry during ergocycling. 31 healthy adults (52% women; age: 26.7±6.3 years; Body Mass Index: 23.9±3.3 kg/m2) completed a 45-min ergocycling session at 50% of their VO2(peak). Despite a significant underestimation of 18.7±13.2 kcal during the first 10 min of the activity (T=5.06; p<0.001), we observed an overall good agreement between energy expenditure estimated by the SenseWear Armband during ergocycling and indirect calorimetry (260.3±80.1 vs. 287.8±97.1 kcal, respectively) (T=-2.148; p=0.04) and a significant intra-class correlation (r=0.81; p<0.001). The results of the present study indicate that the SenseWear Armband underestimated energy expenditure during a 45-min ergocycling session at a 50% VO2(peak) intensity, mainly during the first 10 min. Underestimation at the onset of the activity warrants further research.

Association between physical activity energy expenditure and inflammatory markers in sedentary overweight and obese women.

OBJECTIVE: Chronic subclinical inflammation and regular physical activity have opposing relationships to obesity-related metabolic diseases. Yet, the association between chronic inflammation and physical activity has rarely been examined in obese subjects. We examined the association between physical activity energy expenditure (PAEE), total (TEE) and resting energy expenditure (REE) and cardiorespiratory fitness (VO(2)peak) with inflammatory markers in overweight/obese women. DESIGN: Cross-sectional study. METHODS: The study included 152 overweight/obese postmenopausal women who were sedentary and free of chronic/inflammatory diseases (mean age: 57.5 (95% confidence interval (CI) 56.7-58.3) years, body mass index (BMI): 32.5 (95% CI 31.8-33.2) kg m(-2)). The following parameters were measured: TEE (doubly labeled water), REE (indirect calorimetry), PAEE (as (TEE x 0.90)-REE), VO(2)peak (ergocycle) and serum high-sensitive C-reactive protein (hsCRP), haptoglobin, soluble tumor necrosis factor-α receptor 1 (sTNFR1), interleukin-6, orosomucoid and white blood cells. RESULTS: Sedentary women with the highest tertile of PAEE (1276 (1233-1319) kcal day(-1)) had lower concentrations of hsCRP and haptoglobin than those in the lowest tertile (587 (553-621) kcal day(-1)) after adjustment for fat mass (P<0.05). Soluble TNFR1 was positively correlated with VO(2)peak, TEE and REE (P<0.05), and hsCRP and orosomucoid were positively associated with REE (P<0.01), whereas haptoglobin was negatively associated with PAEE (P<0.05). In stepwise regression analyses that examined the concomitant associations of components of energy expenditure with inflammatory markers, PAEE remained the only predictor of hsCRP and haptoglobin (P<0.05), explaining 14 and 5%, respectively, of their variation,whereas REE was the only predictor of orosomucoid (r (2) = 0.05, P = 0.02) after adjustment for fat mass. Adding leptin to the regression models results in similar relationships between inflammatory markers and components of energy expenditure. CONCLUSION: PAEE is an independent predictor of hsCRP and haptoglobin in sedentary overweight/obese postmenopausal women free of chronic disease. Our data support the role of physical activity in reducing subclinical inflammation and risk of metabolic and cardiovascular diseases.

Determination of bile acids in biological fluids by liquid chromatography-electrospray tandem mass spectrometry.

A simple, sensitive, and specific liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the determination of bile acids in human bile has been developed. The bile acids were extracted with a C(18) (octadecyl) reversed-phase column and identified and quantified by simultaneous monitoring of their parent and daughter ions, using the multiple reaction monitoring mode. Identification and quantification of conjugated bile acids in bile was achieved in 5 min. The detection limit was 1 ng, and the determination was linear for concentrations up to 100 ng. The percent recovery of standards made of single conjugated (glycine and taurine) bile acid or of mixture of glycine- or taurine-conjugated cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, and lithocholic acid averaged 71.73% to 95.92%. The percent recovery of the same standard bile acids was also determined by gas chromatography-mass spectrometry (GC-MS), using the selected ion monitoring mode, and averaged 66% to 96%. A biliary bile acid profile of human gallbladder bile was obtained by LC-MS/MS and GC-MS. The results showed a good correlation between the two techniques and no significant differences between the two methods were observed. The LC-MS/MS method was also used for the analysis of serum, urine, and fecal bile acids. In conclusion, LC-MS/MS is a simple, sensitive, and rapid technique for the analysis of conjugated bile acids in bile and other biological samples. - Perwaiz, S., B. Tuchweber, D. Mignault, T. Gilat, and I. M. Yousef. Determination of bile acids in biological fluids by liquid chromatography-electrospray tandem mass spectrometry. J. Lipid Res. 2001. 42: 114;-119.

Effect of complete sulfation of bile acids on bile formation: role of conjugation and number of sulfate groups.

The effect of complete sulfation of conjugated cholic, chenodeoxycholic and deoxycholic acids on bile formation was investigated in rats. The sulfated bile acids were infused intravenously in stepwise increasing doses (1, 2, 3 and 4 mumol/min/100 gm body wt) in rats after 90 min of bile acid pool depletion. The effects of these bile acids on bile flow, bile salt, biliary phospholipid and cholesterol secretion rates were determined. In addition, their choleretic activity and their effect on biliary lipid secretion were calculated. Appropriate controls infused with nonsulfated bile were also performed. The sulfated bile acids increased bile flow with increasing the infusion doses, and the maximum bile flow was significantly higher than nonsulfated bile acids. Although cholestasis was developed during the infusion of nonsulfated bile acids, no cholestatic effect was observed for sulfated bile acids. With the exception of cholic acid, sulfation significantly increased the bile acid secretory rate maximum. The sulfates of chenodeoxycholic and deoxycholic acids were further hydroxylated. The choleretic activities for all the sulfated bile acids were significantly higher than the nonsulfated bile acids. All the sulfated bile acids significantly reduced the biliary lipid secretion, and a significant correlation was found between the choleretic activity and the phospholipid-dependent bile acid secretion. The data also showed that infusion of sulfated taurine-conjugated bile acids produced higher bile flow and bile acid secretion rate and was less effective when biliary lipid secretion rates were reduced compared with glycine conjugates. It is concluded that sulfated conjugated bile acids may have a role in protection during cholestasis either by stimulation of bile flow or by reduction of biliary lipid secretion, thus protecting cell membranes from the detergent properties of high concentrations of nonsulfated bile acids.

Influence of dehydrocholic acid on the secretion of bile acids and biliary lipids in rats.

This study investigated the influence of dehydrocholic acid (DHCA) infusion on the secretion of endogenous bile acids, and biliary lipids in rats in an attempt to explain the reduction of biliary lipid secretion associated with DHCA infusion. DHCA increased bile flow and the bile acids produced during the infusion were composed of three hydroxy-oxo metabolites (83-93%), and cholic acid (6-14%). Very little DHCA was secreted unchanged (less than 2%). The secretions of all the endogenous biliary bile acids were diminished within 30-60 min of infusion. DHCA furthermore reduced the secretion of exogenous cholic acid when co-infused with DHCA. Phospholipid secretion declined to an undetectable amount and cholesterol declined to 10% of the base value by the end of the infusion. The reduction of biliary lipid secretion during DHCA infusion was attributed to the diminished secretion of endogenous bile acids. These data show that DHCA infusion induces choleresis associated with reduced secretion of endogenous and/or exogenous biliary components.

Effect of coinfusion of cholic acid and sulfated cholic acid on bile formation in rats.

The effect of combined infusion of sulfated cholic acid and nonsulfated cholic acid on bile formation was investigated. The data show that the secretion of sulfated cholic acid is slower and does not share the same transport mechanism(s) as nonsulfated cholic acid. Sulfated cholic acid significantly increased bile flow and reduced the secretion of biliary phospholipids, cholesterol, and protein associated with the secretion of exogenous nonsulfated cholic acid, only when they were infused in a ratio higher than 2:1 (sulfated:nonsulfated). Thus it is concluded that sulfated bile acids may protect the liver against the toxic effect of high concentration of bile acids. The relevance of these findings to human cholestasis remains to be determined because sulfated bile acids do not predominate in serum during cholestasis.