Normal diet NaCl variation can affect the renal set-point for plasma pH-(HCO3-) maintenance

Dietary Contributions to Metabolic Acidosis

Eating a net acid-producing diet can produce an "acid stress" of severity proportional to the diet net acid load, as indexed by the steady-state renal net acid excretion rate. Depending on how much acid or base is ingested or produced from endogenous metabolic processes and how well our homeostatic mechanisms can buffer or eliminate the additional acids or bases, we can alter our systemic acid-base balance. With increasing age, the kidney's ability to excrete daily net acid loads declines (a condition similar to that of mild CKD), invoking increased utilization of potential base stores (eg, bone, skeletal muscle) on a daily basis to mitigate the acid accumulation, thereby contributing to development of osteoporosis, loss of muscle mass, and age-related renal insufficiency. Patients suffering from more advanced CKD often present with more severe acid stress or metabolic acidosis, as the kidney can no longer excrete the entire acid load. Alkaline diets based on fruits and vegetables may have a positive effect on long-term preservation of renal function while maintaining nutritional status. This chapter discusses the biochemistry of dietary precursors that affect acid or base production.

Alkaline salts to counteract bone resorption and protein wasting induced by high salt intake: results of a randomized controlled trial

High sodium chloride (NaCl) intake can induce low-grade metabolic acidosis (LGMA) and may thus influence bone and protein metabolism. We hypothesized that oral potassium bicarbonate (KHCO(3)) supplementation may compensate for NaCl-induced, LGMA-associated bone resorption and protein losses. Eight healthy male subjects participated in a randomized trial with a crossover design. Each of two study campaigns consisted of 5 d of dietary and environmental adaptation followed by 10 d of intervention and 1.5 d of recovery. In one study campaign, 90 mmol KHCO(3)/d were supplemented to counteract NaCl-induced LGMA, whereas the other campaign served as a control with only high NaCl intake. When KHCO(3) was ingested during high NaCl intake, postprandial buffer capacity ([HCO(3)(-)]) increased (P = 0.002). Concomitantly, urinary excretion of free potentially bioactive glucocorticoids [urinary free cortisol (UFF) and urinary free cortisone (UFE)] was reduced by 14% [∑(UFF,UFE); P = 0.024]. Urinary excretion of calcium and bone resorption marker N-terminal telopeptide of type I collagen was reduced by 12 and 8%, respectively (calcium, P = 0.047; N-terminal bone collagen telopeptide, P = 0.044). There was a trend of declining net protein catabolism when high NaCl was combined with KHCO(3) (P = 0.052). We conclude that during high salt intake, the KHCO(3)-induced postprandial shift to a more alkaline state reduces metabolic stress. This leads to decreased bone resorption and protein degradation, which in turn might initiate an anticatabolic state for the musculoskeletal system in the long run.

Role of endothelin-1 in renal regulation of acid-base equilibrium in acidotic humans

Endothelin-1 inhibits collecting duct sodium reabsorption and stimulates proximal and distal tubule acidification in experimental animals both directly and indirectly via increased mineralocorticoid activity. Diet-induced acid loads have been shown to increase renal endothelin-1 activity, and it is hypothesized that increased dietary acid-induced endothelin-1 activity may be a causative progression factor in human renal insufficiency and that this might be reversed by provision of dietary alkali. We sought to clarify, in normal human volunteers, the role of endothelin-1 in renal acidification and to determine whether the effect is dependent on dietary sodium chloride. Acid-base equilibrium was studied in seven normal human volunteers with experimentally induced metabolic acidosis [NH(4)Cl 2.1 mmol·kg body weight (BW)(-1)·day(-1)] with and without inhibition of endogenous endothelin-1 activity by the endothelin A/B-receptor antagonist bosentan (125 BID p.o./day) both during dietary NaCl restriction (20 mmol/day) and NaCl repletion (2 mmol NaCl·kg BW(-1)·day(-1)). During NaCl restriction, but not in the NaCl replete state, bosentan significantly increased renal net acid excretion in association with stimulation of ammoniagenesis resulting in a significantly increased plasma bicarbonate concentration (19.0 ± 0.8 to 20.1 ± 0.9 mmol/l) despite a decrease in mineralocorticoid activity and an increase in endogenous acid production. In pre-existing human metabolic acidosis, endothelin-1 activity worsens acidosis by decreasing the set-point for renal regulation of plasma bicarbonate concentration, but only when dietary NaCl provision is restricted.

Hypoelectrolytemia due to inadequate diet

Rice soup is a traditional Korean food administered to control diarrhea. Useful for short-term control of diarrhea, chronic consumption of this soup can cause problems. We treated an infant who visited our hospital for symptoms of lethargy due to hypoelectrolytemia, which developed from the continuous consumption of rice soup (the upper part of rice ground in water) mixed with a spoonful of milk over a 2-month period to control frequent diarrhea. The case is reported here, together with a brief review of the literature.

Long-term combined treatment with thiazide and potassium citrate in nephrolithiasis does not lead to hypokalemia or hypochloremic metabolic alkalosis

BACKGROUND

Potassium citrate is commonly used in combination with a thiazide diuretic in the medical management of recurrent hypercalciuric nephrolithiasis. However, concerns have been raised that administration of this nonchloride potassium alkali with a kaliuretic and natriuretic agent such as thiazide may not be efficacious in correcting or preventing hypokalemia, and may produce hypochloremic metabolic alkalosis. This retrospective analysis was conducted to determine if these two potential complications are encountered in patients on long-term potassium citrate and thiazide therapy.

METHODS

Data were collected on 95 patients who had been on combination therapy for at least 4 months from the stone clinics of the University of Texas Southwestern Medical Center, Duke University Medical Center, and Ochsner Clinic.

RESULTS

Mean serum potassium concentration remained within normal limits without a significant decrease during combined therapy. Serum chloride was significantly lower from pretreatment but by only 1 mEq/L and remained within normal limits throughout treatment. There was a small increase in serum bicarbonate concentration compared to the baseline level of less than 1 mEq/L at 8 to 12 and 18 to 24 months, but not at other treatment periods.

CONCLUSION

Co-administration of potassium citrate did not induce hypokalemia or hypochloremic metabolic alkalosis in our thiazide-treated patient population.