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Background: Diabetic kidney disease (DKD) is a highly prevalent complication in patients with type 2 diabetes mellitus (T2DM). Patients with DKD exhibit changes in plasma levels of amino acids (AAs) due to insulin resistance, reduced protein intake, and impaired renal transport of AAs. The role of AAs in distinguishing DKD from T2DM and healthy controls has yet to be elucidated. This study aimed to investigate the metabolomic profiling of AAs in the plasma of patients with DKD.Methods: We established an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to detect the plasma levels of the 20 AAs in healthy controls (n = 112), patients with T2DM (n = 101), and patients with DKD (n = 101). The key AAs associated with DKD were identified by orthogonal partial least-squares discriminant analysis (OPLS-DA) models with loading plots, shared and unique structures (SUS) plots, and variable importance in projection (VIP) values. The discrimination accuracies of these key AAs were then determined by analyses of receiver-operating characteristic (ROC) curves.Results: Metabolomic profiling of plasma revealed significant alterations in levels of the 20 AAs in patients with DKD when compared to those in either patients with T2DM or healthy controls. Metabolomic profiling of the 20 AAs showed a visual separation of patients with DKD from patients with T2DM and healthy controls in OPLS-DA models. Based on loading plots, SUS plots, and VIP values in the OPLS-DA models, we identified valine and cysteine as potential contributors to the progression of DKD from patients with T2DM. Histidine was identified as a key mediator that could distinguish patients with DKD from healthy controls. Plasma levels of histidine and valine were decreased significantly in patients with DKD with a decline in kidney function, and had excellent performance in distinguishing patients with DKD from patients with T2DM and healthy controls according to ROC curves.Conclusion: Plasma levels of histidine and valine were identified as the main AAs that can distinguish patients with DKD. Our findings provide new options for the prevention, treatment, and management of DKD.

The objective of this study was to assess the spontaneous oscillations in subjects with hypertension based on the wavelet transform of cerebral oxygenation signal measured with near-infrared spectroscopy (NIRS).Continuous recordings of NIRS and arterial blood pressure (ABP) signals were obtained from simultaneous measurements in 20 healthy subjects (age: 70.8±5.2 years) and 22 subjects with hypertension (age: 72.5±6.8 years).Using spectral analysis based on wavelet transform, five frequency intervals were identified (I, 0.4-2 Hz; II, 0.15-0.4 Hz; III, 0.06-0.15 Hz; IV, 0.02-0.06 Hz and V, 0.005-0.02 Hz). The amplitudes of Δ[Hb] and Δ[HbO2] in intervals I, II and III were significantly higher in hypertensive patients, who have increased mean flow velocity in middle cerebral artery (MCA), compared to that in the healthy subjects (p0.01). The amplitudes of the ABP in frequency intervals III and V were significantly higher in hypertensive patients than in the healthy subjects (p0.01).The present findings revealed that hypertension and increased mean flow velocity in MCA have significant effect on the cerebral oscillations. The higher cerebral oscillations might be related to the intracerebral atherosclerosis in response to systemic hypertension. In addition, the higher spontaneous oscillations in intervals III and V in ABP indicate a metabolic regulation and myogenic response to hypertension.

The study aims to assess the spontaneous oscillations in elderly subjects based on the wavelet transform of cerebral oxygenation (CO) and arterial blood pressure (ABP) signals. Continuous recordings of near-infrared spectroscopy (NIRS) and ABP signals were obtained from simultaneous measurements in 20 young subjects (age: 27.3 ± 7.1 years) and 15 elderly subjects (age: 70.8 ± 5.1 years) at rest. Using spectral analysis based on wavelet transform, five frequency intervals were identified (I, 0.005 to 0.02 Hz; II, 0.02 to 0.06 Hz; III, 0.06 to 0.15 Hz; IV, 0.15 to 0.40 Hz; and V, 0.40 to 2.0 Hz). The average amplitudes of the Δ[HbO2] and tissue oxygenation index in intervals I to V and the relative amplitudes in intervals IV and V were significantly lower in elderly subjects than in young subjects ( P < 0.05). In addition, the relative amplitudes of the ABP in interval I were significantly lower in elderly subjects than in young subjects ( P = 0.016). The present findings suggest the presence of a cerebrovascular degenerative process caused by aging. Spontaneous oscillations in the CO could be used as an indicator of cerebrovascular changes and could be used to identify the risk for cerebrovascular degenerative processes.

This study aims to assess the relationship between spontaneous oscillations in changes in cerebral tissue oxyhemoglobin concentrations (Delta [HbO 2 ]) and arterial blood pressure (ABP) signals in healthy elderly subjects during the resting state using wavelet coherence analysis. Continuous recordings of near-infrared spectroscopy (NIRS) and ABP signals were obtained from simultaneous measurements in 33 healthy elderly subjects (age: 70.7 ± 7.9 years) and 27 young subjects (age: 25.2 ± 3.7 years) during the resting state. The coherence between Delta [HbO 2 ] and ABP oscillations in six frequency intervals (I, 0.4–2 Hz; II, 0.15–0.4 Hz; III, 0.05–0.15 Hz; IV, 0.02–0.05 Hz, V, 0.005–0.0095 Hz and VI, 0.005–0.0095 Hz) was analyzed using wavelet coherence analysis. In elderly subjects, the Delta [HbO 2 ] and ABP oscillations were significantly wavelet coherent in interval I, and wavelet phase coherent in intervals I, II and IV. The wavelet coherence in interval I was significantly higher (p = 0.040), in elderly subjects than in young subjects whereas that in interval V significantly lower (p = 0.015). In addition, the wavelet phase coherence in interval IV was significantly higher in elderly subjects than in young subjects (p = 0.028). The difference in the wavelet coherence of the elderly subjects and the young subjects indicates an altered cerebral autoregulation caused by aging. This study provides new insight into the dynamics of Delta [HbO2] and ABP oscillations and may be useful in identifying the risk for dynamic cerebral autoregulation processes.