Potassium metabolism and gastrointestinal function; a review

Potassium physiology from Archean to Holocene: A higher-plant perspective

In this paper, we discuss biological potassium acquisition and utilization processes over an evolutionary timescale, with emphasis on modern vascular plants. The quintessential osmotic and electrical functions of the K⁺ ion are shown to be intimately tied to K⁺-transport systems and membrane energization. Several prominent themes in plant K⁺-transport physiology are explored in greater detail, including: (1) channel mediated K⁺ acquisition by roots at low external [K⁺]; (2) K⁺ loading of root xylem elements by active transport; (3) variations on the theme of K⁺ efflux from root cells to the extracellular environment; (4) the veracity and utility of the "affinity" concept in relation to transport systems. We close with a discussion of the importance of plant-potassium relations to our human world, and current trends in potassium nutrition from farm to table.

Identification and Characterization of a Novel Association between Dietary Potassium and Risk of Crohn's Disease and Ulcerative Colitis

Background

Recent animal studies have identified that dietary salt intake may modify the risk and progression of autoimmune disorders through modulation of the IL-23/T_H17 pathway, which is critical in the pathogenesis of ulcerative colitis (UC) and Crohn’s disease (CD).

Methods

We conducted a prospective study of U.S. women enrolled in the Nurses’ Health Study (NHS) and NHSII who provided detailed and validated information on diet and lifestyle beginning in 1984 in NHS and 1991 in NHSII. We confirmed incident cases of UC and CD reported through 2010 in NHS and 2011 in NHSII. We used Cox proportional hazards models to calculate hazard ratios and 95% confidence intervals. In a case–control study nested within these cohorts, we evaluated the interaction between single nucleotide polymorphisms (SNPs) in genes involved in T_H17 pathway and dietary potassium on risk of CD and UC. In a cohort of healthy volunteers, we also assessed the effect of supplemental potassium on development of naïve and memory T cells, differentiated with TGFβ1 or T_H17 conditions.

Results

Among a total of 194,711 women over a follow-up of 3,220,247 person-years, we documented 273 cases of CD and 335 cases of UC. Dietary intake of potassium (P_trend = 0.005) but not sodium (P_trend = 0.44) was inversely associated with risk of CD. Although, both dietary potassium and sodium were not significantly associated with risk of UC, there was a suggestion of an inverse association with dietary potassium (P_trend = 0.08). The association of potassium with risk of CD and UC appeared to be modified by loci involved in the T_H17 pathway that have previously been associated with susceptibility to CD, particularly SNP rs7657746 (IL21) (P_interaction = 0.004 and 0.01, respectively). In vitro, potassium enhanced the expression of Foxp3 in both naïve and memory CD4+ T cells via activating Smad2/3 and inhibiting Smad7 in T_H17 cells.

Conclusion

Dietary potassium is inversely associated with risk of CD with both in vitro and gene–environment interaction data suggesting a potential role for potassium in regulating immune tolerance through its effect on Tregs and T_H17 pathway.

Selective review of key perioperative renal-electrolyte disturbances in chronic renal failure patients

The medical care of chronic renal failure patients is often complicated by the comorbid conditions of hypertension and coronary artery disease in the perioperative period. The limitations on solute and water excretion imposed by renal dysfunction increase the susceptibility of this population to both salt deficit and surfeit, as well as hyponatremia and hypernatremia perioperatively. Accurate assessment and successful treatment of these complications in renal failure patients require understanding of the concept of electrolyte-free water, proper utilization of diuretics, and calculated prescription of fluid therapy. The presence of hyperkalemia in the adapted renal failure patient generally indicates a severe reduction in glomerular filtration, such that nonrenal hypokalemic treatments are imperative. IV calcium-based therapy and infusion of insulin with glucose represent the mainstays of immediate therapy, and sodium bicarbonate therapy should be given only when severe acidemia is present. Perioperative aggravation of preexistent hypertension is common. Rebound hypertension attributable to injudicious adjustment of the medical regimen should be diligently searched for first, before any new therapies are recommended. Relief of pain or anxiety may be all that is necessary. Briefly acting calcium channel blocker therapy should not be employed in these cases, and smooth IV control by a variety of agents is preferable, the choice of the agent contingent on the clinical scenario.