Renal net acid excretion and plasma leptin are associated with potentially bioactive free glucocorticoids in healthy lean women

Effects of higher dietary acid load: a narrative review with special emphasis in children

Metabolic effects of high diet acid load (DAL) have been studied for years in adults, although only recently in children. Contemporary diets, especially those of Western societies, owe their acidogenic effect to high animal-origin protein content and low contribution of base-forming elements, such as fruits and vegetables. This imbalance, where dietary acid precursors exceed the body's buffering capacity, results in an acid-retaining state known by terms such as "eubicarbonatemic metabolic acidosis," "low-grade metabolic acidosis," "subclinical acidosis," or "acid stress". Its consequences have been linked to chronic systemic inflammation, contributing to various noncommunicable diseases traditionally considered more common in adulthood, but now have been recognized to originate at much earlier ages. In children, effects of high DAL are not limited to growth impairment caused by alterations of bone and muscle metabolism, but also represent a risk factor for conditions such as obesity, insulin resistance, diabetes, hypertension, urolithiasis, and chronic kidney disease (CKD). The possibility that high DAL may be a cause of chronic acid-retaining states in children with growth impairment should alert pediatricians and pediatric nephrologists, since its causes have been attributed traditionally to inborn errors of metabolism and renal pathologies such as CKD and renal tubular acidosis. The interplay between DAL, overall diet quality, and its cascading effects on children's health necessitates comprehensive nutritional assessments and interventions. This narrative review explores the clinical relevance of diet-induced acid retention in children and highlights the potential for prevention through dietary modifications, particularly by increasing fruit and vegetable intake alongside appropriate protein consumption.

Chronic Sub-Clinical Systemic Metabolic Acidosis - A Review with Implications for Clinical Practice

When arterial serum pH remains near the lower pH limit of 7.35 for protracted periods of time, a low-grade, sub-clinical form of acidosis results, referred to in this review as chronic, sub-clinical, systemic metabolic acidosis (CSSMA). This narrative review explores the scientific basis for CSSMA, its consequences for health, and potential therapeutic interventions. The major etiology of CSSMA is the shift away from the ancestral, alkaline diet which was rich in fruit and vegetables, toward the contemporary, acidogenic 'Westernized' diet characterized by higher animal protein consumption and lack of base forming minerals. Urine pH is reduced with high dietary acid load and may be a convenient marker of CSSMA. Evidence suggests further that CSSMA negatively influences cortisol levels potentially contributing significantly to the pathophysiology thereof. Both CSSMA and high dietary acid load are associated with the risk and prognosis of various chronic diseases. Clinical trials show that CSSMA can be addressed successfully through alkalizing the diet by increasing fruit and vegetable intake and/or supplementing with alkaline minerals. This review confirms the existence of a significant body of evidence regarding this low-grade form of acidosis as well as evidence to support its diverse negative implications for health, and concludes that CSSMA is a condition warranting further research.

Endogenous urinary glucocorticoid metabolites and mortality in prednisolone-treated renal transplant recipients

BACKGROUND

Chronic corticosteroid treatment suppresses HPA-axis activity and might alter activity of 11β hydroxysteroid dehydrogenases (11β-HSD). We aimed to investigate whether the endogenous glucocorticoid production and 11β-HSD activities are altered in prednisolone-treated renal transplant recipients (RTR) compared with healthy controls and whether this has implications for long-term survival in RTR.

METHODS

In a longitudinal cohort of 693 stable RTR and 275 healthy controls, 24-hour urinary cortisol, cortisone, tetrahydrocorisol (THF), allotetrahydrocortisol (alloTHF), and tetrahydrocortisone (THE) were measured using liquid chromatography tandem-mass spectrometry. Twenty-four-hour urinary excretion of cortisol and metabolites were used as measures of endogenous glucocorticoid production; (THF + alloTHF)/THE and cortisol/cortisone ratios were used as measures of 11β-HSD activity.

RESULTS

Urinary cortisol and metabolite excretion were significantly lower in RTR compared with healthy controls (P < .001), whereas (THF + alloTHF)/THE and cortisol/cortisone ratios were significantly higher (P < .001 and P = .002). Lower total urinary metabolite excretion and higher urinary (THF + alloTHF)/THE ratios were associated with increased risk of mortality, independent of age, sex, estimated glomerular filtration rate, C-reactive protein, body surface area, and daily prednisolone dose, respectively.

CONCLUSIONS

Endogenous glucocorticoid production and 11β-HSD activities are altered in prednisolone-treated RTR. Decreased total urinary endogenous glucocorticoid metabolite excretion and increased urinary (THF + alloTHF)/THE ratios are associated with increased risk of mortality.

Twenty-four hour urinary cortisol excretion and the metabolic syndrome in prednisolone-treated renal transplant recipients

Chronic prednisolone treatment in renal transplant recipients (RTR) causes metabolic abnormalities, which cluster in the metabolic syndrome (MS). It also suppresses the hypothalamic-pituitaryadrenal (HPA)-axis. We investigated whether HPA-axis suppression, as measured by 24h urinary cortisol excretion, is associated with presence of the MS and its individual components, in outpatient RTR with a functioning graft for >1year. Urinary cortisol was measured in 24h urine, using LC-MS/MS (LOQ 0.30nmol/L). We included 563 RTR (age 51±12years; 54% male) at median 6.0 [IQR, 2.6-11.5] years post-transplantation. MS was present in 439/563 RTR (78%). Median 24h urinary cortisol excretion was 2.0 [IQR, 0.9-5.1]nmol/24h. Twenty-four hour urinary cortisol excretion was independently associated with MS presence (OR=0.80 [95% CI, 0.66-0.98], P=0.02). It was also independently associated with bodyweight (st.β=-0.11, P=0.007), waist circumference (st.β=-0.10, P=0.01), BMI (st.β=-0.14, P=0.001), fasting triglycerides (st.β=-0.15, P=0.001), diabetes (st.β=-0.12, P=0.005), and number of antihypertensives used (st.β=-0.13, P=0.003). Suppressed HPA-axis activity, as reflected by decreased 24h urinary cortisol excretion, is associated with higher prevalence of MS and its individual components (i.e. central obesity, dyslipidemia, diabetes, hypertension) in prednisolone-treated RTR. Assessment of 24h urinary cortisol excretion by LC-MS/MS may be a tool to monitor metabolic side-effects of prednisolone in RTR.

A Randomized Controlled Trial of the Effects of Febuxostat Therapy on Adipokines and Markers of Kidney Fibrosis in Asymptomatic Hyperuricemic Patients With Diabetic Nephropathy

BACKGROUND

In observational studies, higher uric acid levels are associated with metabolic syndrome, diabetes, and kidney disease.

OBJECTIVE

The objective of this study is to examine whether reduction of plasma uric acid with febuxostat, a xanthine oxido reductase inhibitor, impacts adipose tissue oxidative stress, adipokines, and markers of systemic inflammation or kidney fibrosis.

DESIGN

This was a double-blinded randomized controlled trial.

SETTING

Academic university setting was used.

PATIENTS

Overweight or obese adults with hyperuricemia and type 2 diabetic nephropathy were included.

MEASUREMENTS

Adipose tissue thiobarbituric acid reducing substances (TBARS) and adiponectin concentrations and urinary transforming growth factor-β (TGF-β) were primary endpoints. Plasma C-reactive protein, high molecular weight-adiponectin, interleukin-6, tumor necrosis factor-α, and TBARS and albuminuria were among predefined secondary endpoints.

METHODS

Participants were randomly assigned to febuxostat (n = 40) or matching placebo (n = 40) and followed for 24 weeks.

RESULTS

Baseline plasma uric acid levels were 426 ± 83 µmol/L; 95% completed the study. Estimated glomerular filtration rate (eGFR) declined from 54 ± 17 mL/min/1.73 m² at baseline to 51 ± 17 mL/min/1.73 m² at 24 weeks (P = .05). In separate mixed-effects models, compared with placebo, febuxostat reduced uric acid by 50% (P < .001) but had no significant effects on subcutaneous adipose tissue TBARS (-7.4%, 95% confidence interval [CI], 57.4%-101.4%) or adiponectin (6.7%, 95% CI, 26.0%-53.8%) levels or urinary TGF-β/creatinine ratio (18.0%, 95% CI, 10.0%-54.8%) or secondary endpoints.

LIMITATIONS

Relatively modest sample size and short duration of follow-up.

CONCLUSIONS

In this population with progressive diabetic nephropathy, febuxostat effectively reduced plasma uric acid. However, no detectable effects were observed for the prespecified primary or secondary endpoints.

TRIAL REGISTRATION

The study was registered in clinicaltrials.gov (NCT01350388).

Dietary protein's and dietary acid load's influence on bone health

A variety of genetic, mechano-response-related, endocrine-metabolic, and nutritional determinants impact bone health. Among the nutritional influences, protein intake and dietary acid load are two of the factors most controversially discussed. Although in the past high protein intake was often assumed to exert a primarily detrimental impact on bone mass and skeletal health, the majority of recent studies indicates the opposite and suggests a bone-anabolic influence. Studies examining the influence of alkalizing diets or alkalizing supplement provision on skeletal outcomes are less consistent, which raises doubts about the role of acid-base status in bone health. The present review critically evaluates relevant key issues such as acid-base terminology, influencing factors of intestinal calcium absorption, calcium balance, the endocrine-metabolic milieu related to metabolic acidosis, and some methodological aspects of dietary exposure and bone outcome examinations. It becomes apparent that for an adequate identification and characterization of either dietary acid load's or protein's impact on bone, the combined assessment of both nutritional influences is necessary.

Prepubertal glucocorticoid status and pubertal timing

CONTEXT

Whether prepubertal glucocorticoid status impacts on the timing of puberty is not clear.

OBJECTIVE

The objective of the study was to examine the relationship between prepubertal glucocorticoid status and early or late pubertal markers, independent of adrenarchal and nutritional status.

DESIGN AND PARTICIPANTS

Prospective cohort study of healthy Caucasian children (n = 111, 56 boys) who provided both 24-h urine samples and weighed dietary records 1 and 2 yr before the start of pubertal growth spurt [age at take-off (ATO)].

MEASUREMENTS

Major urinary glucocorticoid and androgen metabolites determined by gas chromatography-mass spectrometry analysis were summed to assess daily overall cortisol (ΣC21) and adrenal androgen secretion; urinary free cortisol and cortisone measured by RIA were summed (UFF+UFE) as an indicator of potentially bioactive free glucocorticoids.

MAIN OUTCOMES

The main outcomes included ATO, age at peak height velocity, age at menarche/voice break, ages at Tanner stage 2 for breast (girls) and genital (boys) development, and pubic hair.

RESULTS

In girls ΣC21, but not UFF+UFE, was associated with pubertal markers after adjusting for overall adrenal androgen, urinary nitrogen, and body fat. Girls with higher ΣC21 (fourth quartile) reached ATO 0.7 yr (P = 0.01) and menarche 0.9 yr later (P = 0.006) than girls with lower ΣC21 (first quartile). The ΣC21 tended to be also positively associated with age at Tanner stage 2 for breast (P = 0.1), Tanner stage 2 for pubic hair (P = 0.1), and age at peak height velocity (P = 0.06). In boys, neither the ΣC21 nor UFF+UFE was related to pubertal timing.

CONCLUSION

An individually higher prepubertal glucocorticoid secretion level, even in physiological range, appears to delay early and late pubertal timing of healthy girls, particularly their onset of pubertal growth spurt and menarche.

Urine volume dependency of specific dehydroepiandrosterone (DHEA) and cortisol metabolites in healthy children

Urine volume should be considered as a confounder when using urinary free cortisol (UFF) and cortisone (UFE) to assess glucocorticoid (GC) status. We aimed to examine whether adrenal androgen (AA) metabolites may be also affected by urine volume in healthy children. To compare the flow dependence of GC and AA metabolites, specific GC metabolites were examined. In 24-h urine samples of 120 (60 boys) healthy children (4-10 yr), steroid profiles were determined by GC-MS analysis, UFF and UFE by radioimmunoassay. To assess daily AA and GC secretion rates, 7 quantitatively most important AA (∑C19) and GC (∑C21) metabolites were summed. Sum of DHEA and its 16α-hydroxylated metabolites were denoted as DHEA&M. Association of urine volume with AA (∑C19, DHEA&M, DHEA, 16α-hydroxy-DHEA, 3β,16α,17β-androstenetriol) and GC (∑C21, UFF, UFE, 6β-hydroxycortisol, 20α-dihydrocortisol) were examined in linear regression models. Among the examined AA metabolites, 16α-hydroxy-DHEA (β=0.56, p<0.0001) and DHEA (β=0.43, p=0.05) showed relatively strong association with urine volume. A trend was seen for ∑C19 (β=0.23, p=0.08), but not for DHEA&M (p>0.1). Regarding GC metabolites, urine volume showed a stronger association with cortisol's direct metabolites, i.e., cortisone, 6β-hydroxycortisol and 20α-dihydrocortisol (β=0.4-0.6, p<0.01) than with cortisol itself (β=0.28, p<0.05). ∑C21 was not associated with urine volume. In conclusion, like UFF and UFE, renal excretion of DHEA, 16α-hydroxy-DHEA, 6β-hydroxycortisol, and 20α-dihydrocortisol may also depend on urine volume. The intrarenal production of the latter three and cortisone might explain their relative strong water-flow-dependency. Total AA or GC secretion marker appears not to be relevantly confounded by urine volume.

Glucocorticoids and body fat associated with renal uric acid and oxalate, but not calcium excretion, in healthy children

In patients with hypercortisolism, who are frequently obese, the prevalence of elevated urinary excretion rates of the potential lithogenic factors (calcium, oxalate, and uric acid) is increased. We examined whether the 24-hour urinary excretion rates of calcium, oxalate, and uric acid are already associated with body fat and endogenous glucocorticoids in healthy free-living children, taking relevant nutritional and acid-base factors into account. Urinary analyte excretions were determined in 24-hour urine samples of 300 healthy children aged 4 to 14 years. Potentially bioactive free glucocorticoids were assessed as urinary free cortisol + urinary free cortisone. Associations of glucocorticoids and percentage body fat with the outcome variables were examined in regression models adjusted for sex, height, growth velocity, urinary volume, net acid excretion, and relevant nutritional factors. Percentage body fat and urinary free cortisol + urinary free cortisone explained most of the growth-independent variation of urinary uric acid and also a relevant part of oxalate, but none of calcium. Net acid excretion, an indicator of endogenous acid production, and dietary protein, salt, and fiber intakes were also variably associated with the outcomes urinary calcium, oxalate, and uric acid. In conclusion, body fatness and potentially bioactive free glucocorticoids (even in the physiologic range) appear to affect urinary excretion rates of oxalate and uric acid, whereas urinary calcium output is more strongly related to dietary factors in healthy children. Our data provide the first in vivo-based evidence that the obesity- or hypercortisolism-associated urolithiasis may be a pathophysiologic continuation of the corresponding endocrine metabolic variations in healthy children.

Daily urinary free cortisol and cortisone excretion is associated with urine volume in healthy children

BACKGROUND

In experimental studies, a high fluid intake and a corresponding high urine volume have been shown to increase renal excretion rates of urinary free cortisol (UFF) and cortisone (UFE) in adults. We aimed to examine whether 24-h UFF and UFE excretion rates are also affected by urine volume in children.

METHODS

In 24-h urine samples of 100 pre-pubertal and 100 pubertal healthy children UFF, UFE, tetrahydrocortisol (THF), 5alpha-tetrahydrocortisol (5alpha-THF), and tetrahydrocortisone (THE) were quantified by RIA. The sum of THF, 5alpha-THF, and THE, the 3 primarily glucuronidated tetrahydrometabolites (GC3), reflects daily cortisol secretion. Associations of urine volume with outcome variables UFF, UFE, and GC3 were examined in both developmental groups using multiple regression models adjusted for sex, body weight and height.

RESULTS

Significant positive associations were observed between 24-h urine volume and UFF and UFE in both groups with the highest explained variation for UFE [partial R(2)=0.11 in pre-pubertal group (P<0.005); partial R(2)=0.15 in pubertal group (P<0.0001)]. However, for outcome GC3, urine volume was not significant in either of the groups.

CONCLUSION

Urinary 24-h excretion rates of UFF and UFE but not of the marker of glucocorticoid secretion are affected by daily urine volume in healthy free-living children. For a specific assessment of associations of UFF and UFE with (patho)physiologically relevant factors, urine volume should be considered as a confounder.

Plant based dietary supplement increases urinary pH

BACKGROUND

Research has demonstrated that the net acid load of the typical Western diet has the potential to influence many aspects of human health, including osteoporosis risk/progression; obesity; cardiovascular disease risk/progression; and overall well-being. As urinary pH provides a reliable surrogate measure for dietary acid load, this study examined whether a plant-based dietary supplement, one marketed to increase alkalinity, impacts urinary pH as advertised.

METHODS

Using pH test strips, the urinary pH of 34 healthy men and women (33.9 +/- 1.57 y, 79.3 +/- 3.1 kg) was measured for seven days to establish a baseline urinary pH without supplementation. After this initial baseline period, urinary pH was measured for an additional 14 days while participants ingested the plant-based nutritional supplement. At the end of the investigation, pH values at baseline and during the treatment period were compared to determine the efficacy of the supplement.

RESULTS

Mean urinary pH statistically increased (p = 0.03) with the plant-based dietary supplement. Mean urinary pH was 6.07 +/- 0.04 during the baseline period and increased to 6.21 +/- 0.03 during the first week of treatment and to 6.27 +/- 0.06 during the second week of treatment.

CONCLUSION

Supplementation with a plant-based dietary product for at least seven days increases urinary pH, potentially increasing the alkalinity of the body.

Dietary, metabolic, physiologic, and disease-related aspects of acid-base balance: foreword to the contributions of the second International Acid-Base Symposium

The role of nutrition in human acid-base homeostasis has gained increasing attention in recent years. Although in healthy humans, homeostatic mechanisms and the kidneys' capacity to excrete acid equivalents can prevent strong diet-induced alterations in blood pH, even moderate increases in blood hydrogen ion levels as a result of unfavorable diet composition can have long-term consequences for the occurrence and progression of a number of diseases. The Second International Acid-Base Symposium, Nutrition-Health-Disease, provided deeper insight and updates in the scientific basis of the relation among diet, acid-base homeostasis, physiology, and pathophysiological consequences.