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We have previously shown that an oral glucose load increased both calciuria and oxaluria while the ingestion of fructose induced a rise in calciuria and a decrease in oxaluria. This latter effect remains unclear and might be linked to the reduced intestinal oxalate absorption subsequent to digestive intolerance in some subjects. Such a hypothesis could be enlightened by the study of a parenteral fructose load. Therefore in 7 healthy subjects, we compared the effects of fructose infusion (F) (15 min iv infusion at 0.185 mmol/kg BW/min) to a control glucose infusion (G) on urinary calcium and oxalate. In this study, glycemia and insulinemia increased less after (F) than after (G) (respectively + 21% vs + 216%, p < 0.001 and + 230% vs + 402%, p < 0.05) and phosphatemia decreased less after (F) than after (G) (-7% vs -14%, p < 0.05). Urinary calcium and oxalate increased only after (F) (respectively + 64%, p < 0.01 and + 60%, p < 0.05). Urinary uric acid, another urolithiasis factor, increased after both (F) and (G) (respectively + 45%; p < 0.01 and + 42%; p < 0.01) but uricemia increased only after (F) (+ 25%; p < 0.01). Our results suggest an additional reason to avoid the use of fructose in parenteral nutrition, particularly in individuals with a known history of either calcium oxalate or urate urolithiasis.

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This study investigated (a) changes in ghrelin and peptide YY (PYY) concentrations during a weight reduction programme and (b) baseline ghrelin and PYY levels as predictors of weight loss in 32 severely obese adolescents (BMI z score = 4.1). Subjects spent an academic year in an institution for childhood obesity. Fasting ghrelin and PYY, leptin, insulin levels and insulin resistance were measured at baseline (month 0) and during the programme (months 3, 6, 9). In addition, 15 normal-weight teenagers served as reference for the baseline assessments. At baseline, obese teenagers had lower ghrelin and PYY concentrations than normal-weight adolescents (P < 0.05). Moreover, they showed significantly higher leptin, insulin levels and homeostasis model assessment (HOMA) (P < 0.0001). During the lifestyle modification, there was a significant decrease in body weight among obese teenagers, associated with an increase in ghrelin (apparent from month 6; P < 0.05), a decrease in leptin (from month 3; P < 0.05) and a decrease in insulin and HOMA (from month 3; P < 0.0001), without any significant change in PYY. Anthropometrical changes were correlated neither with baseline ghrelin levels nor with changes in ghrelin and PYY after the lifestyle modification. However, higher baseline PYY tended to correlate with greater anthropometrical changes (P < 0.1). In adolescents with severe obesity, a long-term combination of supervised aerobic exercises and a balanced diet led to weight reduction and increased ghrelin concentrations, without any change in PYY concentrations. Moreover, baseline PYY concentrations might be considered as predictors of weight loss.