Effects of sodium bicarbonate on nitrogen metabolism and ketone bodies during very low energy protein diets in obese subjects

High sodium chloride intake exacerbates immobilization-induced bone resorption and protein losses

We examined, in immobilization, the effect of a diet high in sodium chloride (NaCl) on bone markers, nitrogen balance, and acid-base status. Eight healthy male test subjects participated in a 14-day head-down-tilt bed rest (HDBR) study. During the bed rest period they received, in a randomized crossover design, a high (7.7 meq Na+/kg body wt per day) and a low (0.7 meq Na+/kg body wt per day) NaCl diet. As expected, 24-h excretion of urinary calcium was significantly greater in the high-NaCl-intake HDBR phase than in the low-NaCl-intake HDBR phase ( P < 0.001). High NaCl intake caused a 43–50% greater excretion of the bone resorption markers COOH- (CTX) and NH2- (NTX) terminal telopeptide of type I collagen in HDBR than low NaCl in HDBR (CTX/NTX: P < 0.001). Serum concentrations of the bone formation markers bone-specific alkaline phosphatase (bAP) and NH2-terminal propeptide of type I procollagen (PINP) were identical in both NaCl intake phases. High NaCl intake led to a more negative nitrogen balance in HDBR ( P < 0.001). Changes were accompanied by increased serum chloride concentration ( P = 0.008), reduced blood bicarbonate ( P = 0.017), and base excess ( P = 0.009) whereas net acid excretion was lower during high than during low NaCl intake in immobilization ( P < 0.001). High NaCl intake during immobilization exacerbates disuse-induced bone and muscle loss by causing further protein wasting and an increase in bone resorption. Changes in the acid-base status, mainly caused by disturbances in electrolyte metabolism, seem to determine NaCl-induced degradation processes.

Effect of HCO3- on glutamine and glucose metabolism in lymphocytes

Lymphocytes play a quantitatively important role in glutamine utilization in the body. We hypothesized that in metabolic acidosis characterized by decreased extracellular HCO3- concentration ([HCO3-]), glutamine utilization by lymphocytes may decrease to compensate partially for the increased uptake of glutamine by the kidneys for ammoniagenesis. This study was therefore designed to quantify the effect of extracellular [HCO3-] on glutamine metabolism in lymphocytes relative to glucose utilization. Mesenteric lymph node lymphocytes were incubated at 37 degrees C for 1 hour in Krebs-Henseleit buffer containing 0, 12.5, and 25 mmol/L HCO3- at a constant pH of 7.4 or 15.7 and 25 mmol/L HCO3- at a constant CO2 concentration of 1.25 mmol/L. Reducing extracellular [HCO3-] from 25 to 12.5 mmol/L at constant pH or from 25 to 15.7 mmol/L at constant CO2 concentration decreased glutamine utilization and the production of glutamate and ammonia. A reduction in [HCO3-] from 12.5 to 0 mmol/L further decreased glutamine utilization, as well as the production of all measured glutamine metabolites. Interestingly, decreasing [HCO3-] from 25 to 0 mmol/L had no significant effect on glucose metabolism, although the production of pyruvate (a minor product of glucose in lymphocytes) was decreased in the absence of medium HCO3-. The contribution of glutamine but not of glucose to lymphocyte adenosine triphosphate (ATP) production was decreased with reduced extracellular [HCO3-]. Thus, glucose was a more important fuel for lymphocytes than was glutamine at low [HCO3-].(ABSTRACT TRUNCATED AT 250 WORDS)

Correction of acidosis in humans with CRF decreases protein degradation and amino acid oxidation

The effect of correction of acidosis in chronic renal failure (CRF) was determined from the kinetics of infused L-[1-13C]leucine. Nine CRF patients were studied before (acid) and after two 4-wk treatment periods of sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) (pH: acid 7.31 +/- 0.01, NaHCO3 7.38 +/- 0.01, NaCl 7.30 +/- 0.01). Leucine appearance from body protein (PD), leucine disappearance into body protein (PS) and leucine oxidation (O) decreased significantly with correction of acidosis (PD: acid 122.4 +/- 6.1, NaHCO3 88.3 +/- 6.9, NaCl 116.2 +/- 9.1 mumol.kg-1.h-1, acid vs. NaHCO3 P < 0.01, NaHCO3 vs. NaCl P < 0.01, acid vs. NaCl NS; PS: acid 109.4 +/- 5.6, NaHCO3 79.0 +/- 6.3, NaCl 101.3 +/- 7.7 mumol.kg-1.h-1, acid vs. NaHCO3 P < 0.01, NaHCO3 vs. NaCl P < 0.01, acid vs. NaCl NS; O: acid 13.0 +/- 1.2, NaHCO3 9.2 +/- 0.9, NaCl 15.0 +/- 1.9 mumol.kg-1.h-1, acid vs. NaHCO3 P < 0.05, NaHCO3 vs. NaCl P < 0.01, acid vs. NaCl NS). There were no significant changes in plasma amino acid concentrations. These results confirm that correction of acidosis in chronic renal failure removes a potential catabolic factor.

Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet

Although it is generally agreed that both ketogenic and nonketogenic very low calorie diets promote weight reduction, there is no consensus on a preference of one diet over the other in regard to protein sparing. In the present study, we compared the effects of isocaloric (600 kcal/d) and isonitrogenous (8 g nitrogen/d) ketogenic (low carbohydrate) and nonketogenic diets on parameters of protein and amino acid metabolism, in 16 morbidly obese women maintained on these diets for 4 weeks while confined to a metabolic ward. Cumulative urinary nitrogen excretion (g/4 wk) was significantly (P less than .01) greater (248 +/- 6 v 207 +/- 12, mean +/- SEM, n = 8), and cumulative nitrogen balance significantly (P less than .02) more negative (-50.4 +/- 4.4 v -18.8 +/- 5.7), during treatment with the ketogenic than with the nonketogenic diet. Plasma leucine concentration (mumol/L) was significantly higher (P less than .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (210 +/- 17 v 150 +/- 8), but not at day 28 (174 +/- 9 v 148 +/- 8). Whole-body rates of leucine oxidation (mmol/h) were significantly higher (P less than .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (1.29 +/- 0.20 v 0.92 +/- 0.10) and at day 28 (1.00 +/- 0.16 v 0.75 +/- 0.10). Conversely, proteolysis, as measured by leucine turnover rate and urinary excretion of 3-methylhistidine, was not significantly different between the diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute acidosis and alkalosis on leucine kinetics in man

The effects of acute pH changes on whole body leucine kinetics (1-13C-leucine infusion technique) were determined in normal subjects. Plasma insulin, glucagon, and growth hormone concentrations were kept constant by somatostatin and replacement infusions of the three hormones. When acidosis was produced by ingestion of NH4Cl (4 mmol kg-1 p.os; n = 8) arterialized pH decreased within 3 h from 7.39 +/- 0.01 to 7.31 +/- 0.01 (P less than 0.001) and leucine plasma appearance increased by 0.13 +/- 0.04 mumol kg-1 min-1 (P less than 0.02); in contrast, when alkalosis was produced by intravenous infusion of 4 mmol kg-1 NaHCO3 (n = 7, pH 7.47 +/- 0.01), leucine plasma appearance decreased by -0.09 +/- 0.04 mumol kg-1 min-1 (P less than 0.01 vs. acidosis). Whole body leucine flux also increased during acidosis compared to alkalosis (P less than 0.05), suggesting an increase in whole body protein breakdown during acidosis. Apparent leucine oxidation increased during acidosis compared to alkalosis (P = 0.05). Net forearm leucine exchange remained unaffected by acute pH changes. Plasma FFA concentrations decreased during acidosis by -107 +/- 67 mumol l-1 (P less than 0.05) and plasma glucose increased by 1.90 +/- 0.25 mmol l-1 (P less than 0.02); in contrast, alkalosis resulted in an increase in plasma FFA by 83 +/- 40 mumol l-1 (P less than 0.02; P less than 0.01 vs. acidosis), suggesting an increase in lipolysis; plasma glucose decreased compared to acidosis (P less than 0.01). The data demonstrate that acute metabolic acidosis and alkalosis, as they occur in clinical conditions, influence protein breakdown, and in the opposite direction, lipolysis.

Effects of bicarbonate supplementation on urinary mineral excretion during very low energy diets

Metabolic acidosis is associated with increased calciuria and ammoniagenesis. This study evaluated the effects of oral sodium bicarbonate (NaHCO3) or combined potassium bicarbonate-calcium carbonate supplementation on urinary mineral excretion during the ketoacidosis of a very-low-energy protein diet. Seventeen healthy obese subjects (BMI: 37.5 +/- 3.2 kg/m2, weight: 100 +/- 3 kg) were given a 1.72 MJ all protein (93 g) liquid formula and a multivitamin-mineral supplement daily for 3 weeks. Subjects in groups 1 (n = 6) and 2 (n = 5) received 16 mmol KCl. In addition, subjects in group 1 received 60 mmol Na+ daily as sodium chloride, subjects in group 2, 60 mmol Na+ as NaHCO3. The subjects in group 3 (n = 6) were given 32 mmol K+ as bicarbonate and 16 mmol Ca++ as carbonate daily. Metabolic acidosis was prevented in groups 2 and 3 with bicarbonate and bicarbonate-carbonate administration. This was reflected in significant curtailment of the augmented ammonium nitrogen excretion found in group 1. The additional oral K+ in group 3 improved K+ balance and probably also inhibited ammoniagenesis. Urine calcium was greater (p less than 0.04) in group 1 subjects, but similar in groups 2 and 3, despite higher calcium intake in group 3. Urinary phosphorus decreased with time in all groups, but more so in the group 2 subjects who received NaHCO3. Acidosis was associated with the reverse effect on urinary magnesium, which decreased in group 1 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of extracellular pH, CO2, and HCO3- on ketogenesis in perfused rat liver

Effects of extracellular pH, CO2, and HCO3- on ketone body production from octanoate were studied in perfused livers from fasted rats. pH was adjusted to 7.1-7.5 by varying perfusate [HCO3-] and [CO2], where brackets denote concentration. At constant 25 mM [HCO3-], total production of beta-hydroxybutyrate (beta-OHB) + acetoacetate (AcAc) was constant from pH 7.1 to 7.5. However, the [beta-OHB]/[AcAc] ratio decreased from 1.60 to 1.00 when pH decreased from 7.3 to 7.1; there was no change at pH 7.4. At constant [CO2], decreasing pH from 7.4 to 7.1 did not alter either total ketogenesis or the [beta-OHB]/[AcAc] ratio. This suggests that high [CO2] rather than low pH was responsible for the alteration in the redox ratio. At constant pH of 7.4, variations in [HCO3-] between 15 and 25 mM did not influence total ketogenesis or the [beta-OHB]/[AcAc] ratio. However, increasing [HCO3-] from 25 to 35 mM decreased the [beta-OHB]/[AcAc] ratio from 1.76 to approximately 1, again without affecting total ketogenesis. At constant 1.75 mM [CO2], increasing [HCO3-] from 25 to 35 mM also reduced the [beta-OHB]/[AcAc] ratio from 1.63 to approximately 1, suggesting that the effect of high [HCO3-] on this redox ratio can be ascribed to HCO3- itself. It is concluded that high [CO2] or [HCO3-] decreases the mitochondrial [NADH]/[NAD+] ratio in hepatocytes, resulting in a decreased [beta-OHB]/[AcAc] ratio.