Department of Urology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium.
Department of Pediatric Nephrology, Ghent University Hospital, Ghent, Belgium.
Eur J Pediatr. 2019 Dec;178(12):1849-1858. doi: 10.1007/s00431-019-03456-y. Epub 2019 Sep 5.
Adolescent obesity is a serious health problem associated with many comorbidities. Obesity-related alterations in circadian rhythm have been described for nocturnal blood pressure and for metabolic functions. We believe renal circadian rhythm is also disrupted in obesity, though this has not yet been investigated. This study aimed to examine renal circadian rhythm in obese adolescents before and after weight loss.In 34 obese adolescents (median age 15.7 years) participating in a residential weight loss program, renal function profiles and blood samples were collected at baseline, after 7 months, and again after 12 months of therapy. The program consisted of dietary restriction, increased physical activity, and psychological support. The program led to a median weight loss of 24 kg and a reduction in blood pressure. Initially, lower diurnal free water clearance (- 1.08 (- 1.40-- 0.79) mL/min) was noticed compared with nocturnal values (0.75 (- 0.89-- 0.64) mL/min). After weight loss, normalization of this inverse rhythm was observed (day - 1.24 (- 1.44-1.05) mL/min and night - 0.98 (- 1.09-- 0.83) mL/min). A clear circadian rhythm in diuresis rate and in renal clearance of creatinine, solutes, sodium, and potassium was seen at all time points. Furthermore, we observed a significant increase in sodium clearance. Before weight loss, daytime sodium clearance was 0.72 mL/min (0.59-0.77) and nighttime clearance was 0.46 mL/min (0.41-0.51). After weight loss, daytime clearance increased to 0.99 mL/min (0.85-1.17) and nighttime clearance increased to 0.78 mL/min (0.64-0.93).Conclusion: In obese adolescents, lower diurnal free water clearance was observed compared with nocturnal values. Weight loss led to a normalization of this inverse rhythm, suggesting a recovery of the anti-diuretic hormone activity. Both before and after weight loss, clear circadian rhythm of diuresis rate and renal clearance of creatinine, solutes, sodium, and potassium was observed.What is Known:• Obesity-related alterations in circadian rhythm have been described for nocturnal blood pressure and for metabolic functions. We believe renal circadian rhythm is disrupted in obesity, though this has not been investigated yet.What is New:• In obese adolescents, an inverse circadian rhythm of free water clearance was observed, with higher nighttime free water clearance compared with daytime values. Weight loss led to a normalization of this inverse rhythm, suggesting a recovery of the anti-diuretic hormone activity.• Circadian rhythm in diuresis rate and in the renal clearance of creatinine, solutes, sodium, and potassium was preserved in obese adolescents and did not change after weight loss.
青少年肥胖是一种与许多合并症相关的严重健康问题。已经描述了与肥胖相关的昼夜节律改变，包括夜间血压和代谢功能。我们认为肾脏的昼夜节律也会在肥胖中被打乱，尽管这尚未得到研究。本研究旨在探讨肥胖青少年减肥前后的肾脏昼夜节律。
在参加住宅减肥计划的 34 名肥胖青少年（中位年龄 15.7 岁）中，在基线、7 个月后和治疗 12 个月后采集肾脏功能谱和血样。该计划包括饮食限制、增加体力活动和心理支持。该计划导致体重平均减轻 24 公斤，血压降低。最初，与夜间值（0.75（-0.89--0.64）mL/min）相比，白天的自由水清除率（-1.08（-1.40--0.79）mL/min）较低。减肥后，这种反向节律恢复正常（白天-1.24（-1.44-1.05）mL/min，夜间-0.98（-1.09--0.83）mL/min）。在所有时间点都观察到利尿率和肌酐、溶质、钠和钾的肾脏清除率的明显昼夜节律。此外，我们观察到钠清除率显著增加。减肥前，白天钠清除率为 0.72 mL/min（0.59-0.77），夜间清除率为 0.46 mL/min（0.41-0.51）。减肥后，白天清除率增加到 0.99 mL/min（0.85-1.17），夜间清除率增加到 0.78 mL/min（0.64-0.93）。
与夜间值相比，肥胖青少年的日间自由水清除率较低。减肥导致这种反向节律正常化，提示抗利尿激素活性恢复。减肥前后均观察到利尿率和肌酐、溶质、钠和钾的肾脏清除率的明显昼夜节律。
在肥胖青少年中，观察到自由水清除率的反向昼夜节律，夜间自由水清除率高于白天值。减肥导致这种反向节律正常化，提示抗利尿激素活性恢复。
肥胖青少年的利尿率和肌酐、溶质、钠和钾的肾脏清除率昼夜节律保持不变，减肥后没有改变。
