Oral sodium bicarbonate in people on haemodialysis: a randomised controlled trial

Background Adverse events and mortality tend to cluster around dialysis sessions, potentially due to the impact of the saw-toothed profile of uraemic toxins such as potassium, peaking pre-dialysis and rapidly dropping during dialysis. Acidosis could be contributing to this harm by exacerbating a rise in potassium. The objectives of this study were to investigate the effects of oral bicarbonate treatment on reducing inter-dialytic potassium gain as well as other clinical consequences of preserving muscle mass and function and reducing intradialytic arrhythmia risk in people on haemodialysis. Methods Open-label randomised controlled trial in a single-centre (London, UK). Forty-three clinically stable adults on haemodialysis were recruited, with a 6 month average pre-dialysis serum bicarbonate level < 22 mmol/l and potassium > 4 mmol/l. Thirty-three participants completed the study. Oral sodium bicarbonate tablets titrated up to a maximum of 3 g bd (6 g total) in intervention group for 12 weeks versus no treatment in the control group. Outcomes compared intervention versus non-intervention phases in the treated group and equivalent time points in the control group: pre- and post-dialysis serum potassium; nutritional assessments: muscle mass and handgrip strength and electrocardiograms (ECGs) pre and post dialysis. Results Participants took an average of 3.7 ± 0.5 g sodium bicarbonate a day. In the intervention group, inter-dialytic potassium gain was reduced from 1.90 ± 0.60 to 1.69 ± 0.49 mmol/l (p = 0.032) and pre-dialysis potassium was reduced from 4.96 ± 0.62 to 4.79 ± 0.49 mmol/l without dietary change. Pre-dialysis bicarbonate increased from 18.15 ± 1.35 to 20.27 ± 1.88 mmol/l, however with an increase in blood pressure. Nutritionally, lean tissue mass was reduced in the controls suggesting less catabolism in the intervention group. There was no change in ECGs. Limitations are small sample size and unblinded study design lacking a placebo, with several participants failing to achieve the target of 22 mmol/l serum bicarbonate levels due mainly to tablet burden. Conclusion Oral sodium bicarbonate reduced bicarbonate loss and potassium gain in the inter-dialytic period, and may also preserve lean tissue mass. Trial registration The study was registered prospectively on 06/08/2015 with EU Clinical Trials Register EudraCT number 2015-001439-20.

Salt-Sensitivity of Volume and Blood Pressure in a Mouse with Globally Reduced ENaC γ Subunit Expression

The epithelial Na+ channel (ENaC) promotes the absorption of Na+ in the aldosterone-sensitive distal nephron, colon, and respiratory epithelia. Deletion of genes encoding ENaC's subunits results in early post-natal mortality. We present initial characterization of a mouse with dramatically suppressed expression of ENaC's γ subunit. We used this hypomorphic (γmt) allele to explore the importance of this subunit in homeostasis of electrolytes and body fluid volume. At baseline, γ subunit expression in γmt/mt mice was markedly suppressed in kidney and lung, while electrolytes resembled those of littermate controls. Aldosterone levels in γmt/mt mice exceeded those seen in littermate controls. Quantitative magnetic resonance (QMR) measurement of body composition revealed similar baseline body water, lean tissue mass, and fat tissue mass in γmt/mt mice and controls. γmt/mt mice exhibited a more rapid decline in body water and lean tissue mass in response to a low Na+ diet than controls. Replacement of drinking water with 2% saline selectively and transiently increased body water and lean tissue mass in γmt/mt mice, relative to controls. Lower blood pressures were variably observed in γmt/mt mice on a high salt diet, compared to controls. γmt/mt also exhibited reduced diurnal blood pressure variation, a "non-dipping" phenotype, on a high Na+ diet. While ENaC in renal tubules and colon work to prevent extracellular fluid volume depletion, our observations suggest that ENaC in other tissues may participate in regulating extracellular fluid volume and blood pressure.

Abstract P330: Growth Differentiation Factor 15 Causes Cardiac Cachexia In Heart Failure

Background: Cachexia is wasting of normal body tissue and occurs in chronic medical diseases. It is a common complication of heart failure (HF) that is associated with very high mortality. Growth differentiation factor 15 (GDF15) regulates food intake and can cause cancer cachexia. GDF15 is a sensitive biomarker in humans, though its biologic function in HF is unknown. This study investigated the role of GDF15 in HF. Methods: We utilized a genetic mouse model of dilated cardiomyopathy (DCM) caused by a mutation in the phospholamban gene (PLN R9C ). PLN R9C mice have dysregulated cardiac calcium handling (a common feature of nearly all forms of HF) and develop progressive DCM that leads to HF and premature death. Q-PCR and ELISA were performed to assess expression, tissue distribution and circulating levels of GDF15 in PLN R9C and age-matched wild type (WT) mice. A double transgenic mouse was created by crossing our DCM model with a constitutive Gdf15 knock-out (KO). Using this novel model, we quantified food intake, and assessed fat and lean tissue mass by tissue weight at necropsy and by dual-energy X-ray absorptiometry (DXA). Cardiac function was assessed using echocardiography, and histochemistry performed to quantify cardiac fibrosis. Survival was assessed by Kaplan-Meier. Results: GDF15 mRNA (43-fold; p<0.01) and protein (54-fold; p<0.01) were increased in LV tissue, and circulating GDF15 was elevated (8.3-fold; p=0.03) in PLN R9C mice. Gdf15 was expressed at low levels and was not increased in other organs in PLN R9C mice. PLN R9C mice developed cachexia (reduced fat and lean mass by tissue weight, reduced fat mass by DXA vs. WT; p<0.01 for all) and consumed less food (p<0.01 vs. WT). Gdf15 KO in PLN R9C preserved fat and lean tissue mass and resulted in higher food intake (p≤0.01 for all). Gdf15 KO had no effect on cardiac structure or function by echocardiography and PLN R9C / Gdf15 KO mice displayed only a small reduction in cardiac fibrosis relative to PLN R9C mice (3%; p<0.01). Despite this, Gdf15 KO prolonged survival in PLN R9C (29±3 vs. 25±3 weeks; p<0.01). Conclusions: GDF15 is a novel cardiac hormone produced in HF that triggers anorexia and cachexia in HF by an extra-cardiac mechanism.

Body Composition of Chronic Kidney Disease Patients

With accelerated muscle proteolysis, a decrease in muscle mass is evident in chronic kidney disease (CKD) patients. This eventually leads to nutritional disturbance that for a long has been mostly attributed to malnutrition. This predisposes patients to premature morbidity and mortality. Assessing body composition, thus, becomes vital. In this cross-sectional study, CKD patients (n = 47) of stages 2, 3a, 3b and 4 were assessed for their lean tissue mass, adipose tissue mass and overhydration by body composition monitor. Lean tissue index and fat tissue index were calculated as lean tissue mass and adipose tissue mass in kilogram divided by patients’ height in square meters. Patients were assessed for their handgrip strength (HGS) by Jamar hydraulic hand dynamometer, and also for their 7-day diet history. Mean lean tissue index of CKD patients was 11.73 ± 2.49 kg/m2. About 34 (72.3%) out of 47 patients were below the reference value of lean tissue index. A significant difference in lean tissue index (P = 0.03) was observed at various stages. Patients at stage 4 had the lowest lean tissue index. Lean tissue was significantly (P = 0.03) low in patients consuming protein <0.6 gm/kg/day. All 47 patients had less than normal HGS values. Patients’ mean fat tissue index was 14.86 ± 6.18 kg/m2 and had water retention with a mean overhydration of 1.47 ± 2.12 L. CKD patients were malnourished with a significant low lean tissue index. Dietary protein intake and HGS of these patients were positively associated with lean tissue index.

Meta-Analysis Examining the Importance of Creatine Ingestion Strategies on Lean Tissue Mass and Strength in Older Adults

Creatine supplementation in conjunction with resistance training (RT) augments gains in lean tissue mass and strength in aging adults; however, there is a large amount of heterogeneity between individual studies that may be related to creatine ingestion strategies. Therefore, the purpose of this review was to (1) perform updated meta-analyses comparing creatine vs. placebo (independent of dosage and frequency of ingestion) during a resistance training program on measures of lean tissue mass and strength, (2) perform meta-analyses examining the effects of different creatine dosing strategies (lower: ≤5 g/day and higher: >5 g/day), with and without a creatine-loading phase (≥20 g/day for 5–7 days), and (3) perform meta-analyses determining whether creatine supplementation only on resistance training days influences measures of lean tissue mass and strength. Overall, creatine (independent of dosing strategy) augments lean tissue mass and strength increase from RT vs. placebo. Subanalyses showed that creatine-loading followed by lower-dose creatine (≤5 g/day) increased chest press strength vs. placebo. Higher-dose creatine (>5 g/day), with and without a creatine-loading phase, produced significant gains in leg press strength vs. placebo. However, when studies involving a creatine-loading phase were excluded from the analyses, creatine had no greater effect on chest press or leg press strength vs. placebo. Finally, creatine supplementation only on resistance training days significantly increased measures of lean tissue mass and strength vs. placebo.

Skeletal Muscle Health in Polycystic Ovary Syndrome: Protective Effect of Hyperandrogenism or Detrimental Effect of Insulin Resistance? A Systematic Review and Meta-Analysis

Women with polycystic ovary syndrome (PCOS) exhibit reduced skeletal muscle insulin-mediated glucose uptake. Altered muscle mass may affect insulin resistance (IR) and inflammation, thereby potentially aggravating reproductive status including ovulatory cyclicity and fertility potential. However, the relationship between PCOS and skeletal muscle mass is elusive given conflicting reports on protective or detrimental influence of PCOS endocrine derangements (hyperandrogenism, IR) on muscle. We evaluated whether muscle mass and function are affected by PCOS in response to a call to elucidate musculoskeletal alterations in the International Evidence-based Guideline for the Assessment and Management of PCOS. Databases of MEDLINE, Web of Science, and Scopus were searched (January 1990 to September 2020) to identify observational studies on skeletal muscle mass (lean tissue mass) and function (strength) in PCOS and control groups. The primary outcome was total lean body mass (LBM) or fat-free mass (FFM). Data were pooled by random-effects models and expressed as weighted mean differences and 95% confidence intervals. Forty-five studies (n = 3,676 [1,854, PCOS; 1,822, controls]) were eligible. Forty-one evaluated lean tissue mass and five strength. PCOS groups had increased total (0.83 [0.08, 1.58] kg; P=0.03; I2 = 72.0%) yet comparable trunk (0.84 [-0.37, 2.05] kg; P = 0.15; I2 = 73.0%) LBM/FFM. There were no associations between mean differences of groups in total testosterone (TT) or homeostatic model assessment of IR (HOMA-IR) and total/trunk LBM/FFM (All: P ≥ 0.75) by meta-regressions. However, mean differences of groups in body mass index (BMI) were associated with total (0.65 [0.23, 1.06] kg; P &lt; 0.01; I2 = 56.9%) and trunk (0.56 [0.11, 1.01] kg; P = 0.02; I2 = 42.8%) LBM/FFM. Accordingly, PCOS sub-group with overweight/obesity (BMI ≥ 25 kg/m2) exhibited greater total LBM/FFM than controls (1.58 [0.82, 2.34] kg; P &lt; 0.01; I2 = 64.0%) unlike a lean (BMI &lt; 25 kg/m2) sub-group (-0.45 [-1.94, 1.05] kg; P = 0.53; I2 = 69.5%). Some study results were contradictory (i.e., increased appendicular mass or strength in PCOS group or comparable findings between groups) and study methodology varied; thus, inclusion in meta-analyses was not possible. PCOS cohorts have a tendency for increased total and trunk lean tissue mass likely attributed to obesity. However, most critically, whether PCOS influences other lean tissue areas (appendicular), morphology, and function is unclear. Our observations do not support any protective/detrimental influence of hyperandrogenism (TT) or IR (HOMA-IR) on lean mass. Heterogeneity among studies warrants research to address any contributions of lifestyle, healthcare, and biological factors to observed differences for future guideline recommendations to improve PCOS musculoskeletal and reproductive health (www.crd.york.ac.uk/PROSPERO ID, CRD42020203490).

Water and Electrolyte Homeostasis in a Mouse Model with Reduced ENaC Gamma Subunit Expression

The epithelial Na+ channel (ENaC) promotes the absorption of Na+ in the aldosterone-sensitive distal nephron, colon, and respiratory epithelia. Deletion of genes encoding ENaC’s subunits results in early post-natal mortality. We present initial characterization of a mouse with dramatically suppressed expression of the γ subunit. We use this hypomorphic (γmt) allele to explore the importance of ENaC’s γ subunit in homeostasis of electrolytes and body fluid volume. At baseline, γ subunit expression in γmt/mt mice is markedly suppressed in kidney and lung, while electrolytes resemble those of littermate controls. Challenge with a high K+ diet does not cause significant differences in blood K+, but provokes higher aldosterone in γmt/mt mice than controls. Quantitative magnetic resonance (QMR) measurement of body composition reveals similar baseline body water, lean tissue mass, and fat tissue mass in γmt/mt mice and controls. Surprisingly, euvolemia is sustained without significant changes in aldosterone or atrial natriuretic peptide. γmt/mt mice exhibit a more rapid decline in body water and lean tissue mass in response to a low Na+ diet than controls. Replacement of drinking water with 2% saline induces dramatic increases in body fat in both genotypes, and a selective transient increase in body water and lean tissue mass in γmt/mt mice. While ENaC in renal tubules and colon work to prevent extracellular fluid volume depletion, our observations suggest that ENaC in non-epithelial tissues may have a role in preventing extracellular fluid volume overload.

Body composition monitoring in children and adolescents: reproducibility and reference values

There is an increasing need for suitable tools to evaluate body composition in paediatrics. The Body Composition Monitor (BCM) shows promise as a method, but reference values in children are lacking. Twenty children were included and measured twice by 4 different raters to asses inter- and intra-rater reproducibility of the BCM. Reliability was assessed using the Bland-Altman method and by calculating intraclass correlation coefficients (ICCs). The intra-rater ICCs were high (≥ 0.97) for all parameters measured by BCM as were the inter-rater ICCs for all parameters (≥ 0.98) except for overhydration (0.76). Consequently, a study was set up in which BCM measurements were performed in 2058 healthy children aged 3–18.5 years. The age- and gender-specific percentile values and reference curves for body composition (BMI, waist circumference, fat mass and lean tissue mass) and fluid status (extracellular and intracellular water and total body water) relative to age were produced using the GAMLSS method for growth curves.Conclusion: A high reproducibility of BCM measurements was found for fat mass, lean tissue mass, extracellular water and total body water. Reference values for these BCM parameters were calculated in over 2000 children and adolescents aged 3 to 18 years. What is Known• The 4-compartment model is regarded as the ‘gold standard’ of body composition methods, but is inappropriate for regular follow-up or screening of large groups, because of associated limitations. • Body Composition Monitor® is an inexpensive field method that has the potential to be an adequate monitoring tool.What is New• Good reproducibility of BCM measurements in children provides evidence to use the device in longitudinal follow-up, multicentre and comparative studies.• Paediatric reference values relative to age and sex for the various compartments of the body are provided.