Plasma bicarbonate and risk of type 2 diabetes mellitus

Dietary acid load in health and disease

Maintaining an appropriate acid-base equilibrium is crucial for human health. A primary influencer of this equilibrium is diet, as foods are metabolized into non-volatile acids or bases. Dietary acid load (DAL) is a measure of the acid load derived from diet, taking into account both the potential renal acid load (PRAL) from food components like protein, potassium, phosphorus, calcium, and magnesium, and the organic acids from foods, which are metabolized to bicarbonate and thus have an alkalinizing effect. Current Western diets are characterized by a high DAL, due to large amounts of animal protein and processed foods. A chronic low-grade metabolic acidosis can occur following a Western diet and is associated with increased morbidity and mortality. Nutritional advice focusing on DAL, rather than macronutrients, is gaining rapid attention as it provides a more holistic approach to managing health. However, current evidence for the role of DAL is mainly associative, and underlying mechanisms are poorly understood. This review focusses on the role of DAL in multiple conditions such as obesity, cardiovascular health, impaired kidney function, and cancer.

The еffects of low mineral content water on microbiota, metabolic, and oxidative stress parameters in patients with type 2 diabetes mellitus

Although scientific evidence has shown that natural mineral waters have potential beneficial metabolic effects, there is still very scarce data on their influence on type 2 diabetes mellitus (T2DM). The study was designed to investigate the effects of low mineral water from the "Sneznik-1/79″ source in Serbia on microbiota, metabolic, and oxidative stress parameters in patients with T2DM. In total, 60 patients with confirmed T2DM were included in the study, and they consumed "Sneznik-1/79″ water for 28 days. To examine the positive effects of "Sneznik-1/79″ water, we compared the results before and after the four weeks of "Sneznik-1/79″ water intake. Standard biochemical analyses were carried out, such as glucose level, lipid profile, and stool tests. The blood samples were collected to evaluate the effects of "Sneznik-1/79″ water on the redox status. At the end of the monitoring period, the total cholesterol concentration significantly dropped compared to the initial value. A significant improvement in intestinal peristalsis was observed, which was reflected in the fact that after four weeks, all patients established regular, daily bowel movements. Moreover, consumption of "Sneznik-1/79″ water eliminated the appearance of dysbiosis in 50% of patients. Additionally, the antioxidant capacity was improved by increasing the concentration of superoxide dismutase and reduced glutathione. The result of our study pointed out that the intake of "Sneznik-1/79″ water could be a promising adjuvant therapy for improving intestinal peristalsis as well as reducing the appearance of dysbiosis in T2DM patients.

Hidden chronic metabolic acidosis of diabetes type 2 (CMAD): Clues, causes and consequences

Interpretation of existing data revealed that chronic metabolic acidosis is a pathognomic feature for type 2 diabetes (T2D), which is described here as "chronic metabolic acidosis of T2D (CMAD)" for the first time. The biochemical clues for the CMAD are summarised in the following; low blood bicarbonate (high anionic gap), low pH of interstitial fluid and urine, and response to acid neutralization, while the causes of extra protons are worked out to be; mitochondrial dysfunction, systemic inflammation, gut microbiota (GM), and diabetic lung. Although, the intracellular pH is largely preserved by the buffer system and ion transporters, a persistent systemic mild acidosis leaves molecular signature in cellular metabolism in diabetics. Reciprocally, there are evidences that CMAD contributes to the initiation and progression of T2D by; reducing insulin production, triggering insulin resistance directly or via altered GM, and inclined oxidative stress. The details about the above clues, causes and consequences of CMAD are obtained by searching literature spanning between 1955 and 2022. Finally, the molecular bases of CMAD are discussed in details by interpretation of an up-to-date data and aid of well constructed diagrams, with a conclusion unravelling that CMAD is a major player in T2D pathophysiology. To this end, the CMAD disclosure offers several therapeutic potentials for prevention, delay or attenuation of T2D and its complications.

You are What You Drink? How Associations Between Profiles of Beverage Consumption and Type 2 Diabetes Risk are Mediated by Biomarker Networks

BACKGROUND

Multiple studies have independently investigated the associations of the consumption of individual beverage types and specific plasma biomarkers with the risk of type 2 diabetes (T2D). However, as individuals do not consume single beverage types exclusively and plasma biomarkers do not act in isolation, it remains unclear how patterns of beverage consumption and plasma biomarker networks associate both with each other and T2D risk.

OBJECTIVES

We aimed to elucidate potential dietary determinants of T2D risk by defining a model that describes habitual beverage consumption profiles in relation to identified networks of circulating plasma biomarkers.

METHODS

This study included 1,461 case and 1,568 control participants from case-control studies of T2D nested within the Nurses' Health Study. Participants completed validated semiquantitative food frequency questionnaires that assessed habitual beverage consumption, and they provided blood samples from which 27 plasma biomarkers of cardiometabolic risk were identified. Common exploratory factor analysis (EFA) identified factors that separately described beverage consumption profiles and biomarker networks. Multivariable-adjusted regression elucidated the relationships between beverage and biomarker factors and T2D risk.

RESULTS

EFA revealed five factors describing unique beverage consumption profiles and seven factors describing biomarker networks. The factor describing alcoholic beverage consumption was associated with a reduced risk of T2D (odds ratio [OR]: 0.50 [0.40, 0.64], P<0.001) mediated, in part, by the factor describing increased concentrations of adiponectin biomarkers (19.9% [12.0, 31.1] P = 0.004). The factor describing low-calorie sweetened beverage (LCSBs) consumption was associated with an increased risk of T2D (OR: 1.33 [1.03, 1.72], P = 0.021), and the factor describing lower concentrations of insulin-like growth factor binding proteins 1 and 2, and soluble leptin receptor, and increased leptin concentrations (P = 0.005).

CONCLUSIONS

Moderate alcohol consumption was associated with reduced T2D risk, mediated in part by increased circulating adiponectin. LCSB consumption was associated with both increased T2D risk and perturbed insulin-like growth factor and leptin signaling.

Association Between Serum Bicarbonate Levels and Prediabetes and Subclinical Inflammation in Young Healthy Adults: A Cross-sectional Study

PURPOSE

Low bicarbonate, a hallmark of metabolic acidosis is associated with various diseases. This study investigated associations between bicarbonate levels with prediabetes and subclinical inflammation among healthy young adults in Qatar.

PATIENTS AND METHODS

A cross-sectional study was carried out with 825 participants aged 18-40 years, devoid of any known comorbidities, using data from the Qatar Biobank. For each participant, blood samples were taken for measurements of bicarbonate, prediabetes, and subclinical inflammation biomarkers. Prediabetes was defined using HbA1c between 5.7 and 6.4% and subclinical inflammation was defined using monocyte to high density lipoprotein (HDL) cholesterol ratio (MHR). Associations between bicarbonate levels and the outcomes were analyzed using multivariable linear and logistic regression and then stratified by gender.

RESULTS

A total of 825 participants with mean age 29.2 years (5.9) of which 365 (44.2%) were males. After multivariable logistic regression, each unit increase in serum bicarbonate was associated with a 17% decreased risk of prediabetes (OR: 0.83, 95%CI: 0.70-0.99, p=0.034), in males but no association was observed for females. Similarly, after multivariable linear regression, a unit increase in serum bicarbonate was associated with a 0.18 unit decrease in MHR (beta -0.18, 95%CI: -0.29, -0.07, p=0.002), again with no association observed in females.

CONCLUSION

In a healthy young adult population, higher serum bicarbonate levels were inversely associated with both prediabetes and subclinical inflammation in males, but not in females.

Association between vitamin D serum levels and insulin resistance assessed by HOMA-IR among non-diabetic adults in the United States: Results from NHANES 2007-2014

Insulin resistance, a pathological response to insulin hormone in insulin-dependent cells, is characterized by the presence of high glucose and insulin concentrations. The homeostasis model of insulin resistance (HOMA-IR) is one of the most used indexes to estimate insulin resistance by assessing the fasting glucose and insulin levels. An association was observed between vitamin D levels and insulin resistance, which varied in different ethnic groups, and there is some evidence that vitamin D supplementation could contribute to the improvement of insulin resistance. This study assessed the association between 25-hydroxyvitamin D (25[OH]D) concentration and HOMA-IR in American adults aged 20 years and older, without diabetes and other chronic diseases that can influence insulin resistance. The data from the National Health and Nutrition Examination Survey (NHANES) 2007–2014 were used by exploiting the free and publicly-accessible web datasets. Linear regression models were performed to evaluate the association between serum 25(OH)D concentration and HOMA-IR, and a negative association was observed, which remained significant following the adjustment for age, gender, race/ethnicity, education, body mass index (BMI), physical activity, the season of examination, current smoking, hypertension, the use of drugs which can influence insulin resistance, serum bicarbonates, triglycerides, and calcium and phosphorus levels. Only in non-Hispanic Blacks was this inverse association between vitamin D and HOMA-IR not observed in the fully adjusted model. Further studies are needed to explain the mechanisms of the observed ethnic/racial differences in the association of vitamin D levels with HOMA-IR.

Base excess is associated with the risk of all-cause mortality in critically ill patients with acute myocardial infarction

Background

Base excess (BE) represents an increase or decrease of alkali reserves in plasma to diagnose acid-base disorders, independent of respiratory factors. Current findings about the prognostic value of BE on mortality of patients with acute myocardial infarction (AMI) are still unclear. The purpose of this study was to explore the prognostic significance of BE for short-term all-cause mortality in patients with AMI.

Methods

A total of 2,465 patients diagnosed with AMI in the intensive care unit from the Medical Information Mart for Intensive Care III (MIMIC-III) database were included in our study, and we explored the association of BE with 28-day and 90-day all-cause mortality using Cox regression analysis. We also used restricted cubic splines (RCS) to evaluate the relationship between BE and hazard ratio (HR). The primary outcomes were 28-day and 90-day all-cause mortality.

Results

When stratified according to quantiles, low BE levels at admission were strongly associated with higher 28-day and 90-day all-cause mortality. Multivariable Cox proportional hazard models revealed that low BE was an independent risk factor of 28-day all-cause mortality [HR 4.158, 95% CI 3.203–5.398 (low vs. normal BE) and HR 1.354, 95% CI 0.896–2.049 (high vs. normal BE)] and 90-day all-cause mortality [HR 4.078, 95% CI 3.160–5.263 (low vs. normal BE) and HR 1.369, 95% CI 0.917–2.045 (high vs. normal BE)], even after adjustment for significant prognostic covariates. The results were also consistent in subgroup analysis. RCS revealed an “L-type” relationship between BE and 28-day and 90-day all-cause mortality, as well as adjusting for confounding variables. Meanwhile, Kaplan–Meier survival curves were stratified by combining BE with carbon dioxide partial pressure (PaCO2), and patients had the highest mortality in the group which had low BE (&lt; 3.5 mEq/L) and high PaCO2 (&gt; 45 mmHg) compared with other groups.

Conclusion

Our study revealed that low BE was significantly associated with 28-day and 90-day mortality in patients with AMI and indicated the value of stratifying the mortality risk of patients with AMI by BE.

Dietary acid load and mortality from all causes, CVD and cancer: results from the Golestan Cohort Study

Given the limited studies and controversial results on association between dietary acid load and mortality from CVD and cancers, we aimed to investigate this association in a large population cohort study in Middle East, with a wide range of dietary acid load. The study was conducted on the platform of the Golestan Cohort Study (GCS), which enrolled 50 045 participants in 2004-2008. Dietary intake was assessed using a validated FFQ. Dietary potential renal acid load (PRAL) score was calculated from nutrient intake. Death and its causes were identified and confirmed by two or three physicians. Cox proportional hazards regression was used to estimate hazard ratio (HR) and 95 % CI for total and cause-specific mortalities. Then, the associations were modelled using restricted cubic splines. PRAL range was -57·36 to +53·81 mEq/d for men and -76·70 to +49·08 for women. During 555 142 person-years of follow-up, we documented 6830 deaths, including 3070 cardiovascular deaths, 1502 cancer deaths and 2258 deaths from other causes. For overall deaths, in final model after adjustment for confounders, participants in the first and fifth quintiles of PRAL had a higher risk of mortality compared with the second quintile of PRAL (HR: 1·08; 95 % CI1·01, 1·16 and HR: 1·07; 95 % CI 1·01, 1·15, respectively); Pfor trend < 0·05). Participants in the first and fifth quintiles of PRAL had a 12 % higher risk of CVD mortality compared with the Q2 of PRAL (HR: 1·12; 95 % CI 1·01-1·25 and HR: 1·12; 95 % CI 1·01, 1·26, respectively; Pfor trend < 0·05). We found that all-cause and CVD mortality rates were higher in the lowest and highest PRAL values, in an approximately U-shaped relation (P-values for the overall association and the non-linear association of energy-adjusted PRAL with total mortality were < 0·001 and < 0·001, and with CVD mortality were 0·008 and 0·003, respectively). Our results highlight unfavourable associations of high acidity and alkalinity of diet with the increased total and CVD mortality risk. It may be important to consider a balanced acid-base diet as a protective strategy to prevent pre-mature death, especially from CVD.

High bicarbonate concentration increases glucose-induced insulin secretion in pancreatic β-cells

Low serum bicarbonate is closely related to type 2 diabetes mellitus. However, the precise role of bicarbonate on glucose homeostasis and insulin secretion remains unknown. In this study, we investigated the effects of bicarbonate concentration on pancreatic β-cells. It was observed that the high bicarbonate concentration of the cell culture medium significantly increased the glucose-induced insulin secretion (GSIS) levels in mouse islets, MIN6, and the INS-1E β cells. MIN6 cells presented an impaired GSIS; the cells produced a lower bicarbonate concentration when co-cultured with Capan-1 than when with CFPAC-1. NBCe1, a major bicarbonate transporter was observed to block the increasing insulin secretions, which were promoted by a high concentration of bicarbonate. In addition, higher extracellular bicarbonate concentration significantly increased the intracellular cAMP level, pHi, and calcium concentration with a 16.7 mM of glucose stimulation. Further study demonstrated that a low concentration of extracellular bicarbonate significantly impaired the functioning of pancreatic β cells by reducing coupling Ca²⁺ influx, whose process may be modulated by NBCe1. Taken together, our results conclude that bicarbonate may serve as a novel target in diabetes prevention-related research.

Diet-dependent acid load associates with mean arterial pressure in a cohort of non-obese, non-black, post-menopausal women

Higher sodium (Na+) intakes are associated with higher blood pressure (BP). Whether this relationship is stronger with diet-dependent acid load (DAL) and in patients with diagnosed hypertension or normal BP is not well determined. We studied 170 postmenopausal women randomized to potassium bicarbonate or placebo till 36 months where 24-hour urine and arterialized blood were collected. We investigated the association of DAL estimated as urinary potential renal acid load (UPRAL) and mean arterial pressure (MAP) using mixed-effects model, adjusting for age, anthropometrics, creatinine clearance, and treatment. Adjusted regression estimates for change in Na+ and UPRAL on MAP after 12 months follow-up were calculated, and further adjustments were made for change in potassium (K+) and body mass index (BMI). MAP was inversely associated with UPRAL (β [95% CI]:-0.11[-0.25,-0.001]). There was effect modification by hypertension (p-interaction=0.04); MAP decreased significantly in normotensives but the association was not significant in hypertensives. A decrease of 0.70 mmHg in MAP (0.13,1.69) per 50 mmol/24 hr reduction in Na+ was noted when the model was adjusted for change in K+. Our results with UPRAL exhibited stronger dose-response for MAP, which remained significant after adjustment for BMI. UPRAL was independently associated with MAP even after adjustment for potential confounders, and the data showed this association to be more pronounced in normotensives. Novelty: • First longitudinal study on the association of UPRAL and MAP • Association was a more robust relationship than between U[Na/K] ratio and MAP • UPRAL may play a significant role in the pathogenesis of primary hypertension.

Obesity and the Risk of Low Bicarbonate: A Cohort Study

Rationale & Objective

Acid retention may occur in the absence of overt metabolic acidosis; thus it is important to identify populations at risk. Because obesity may alter renal acid-base handling, we sought to determine whether overweight and obesity are associated with increased risk for low serum bicarbonate levels, suggesting metabolic acidosis.

Study Design

Retrospective cohort study.

Setting & Participants

Adult patients (n = 96,147) visiting outpatient clinics in the Bronx, NY, between January 1, 2010, and December 31, 2015.

Predictor

Body mass index (BMI).

Outcome

Low serum bicarbonate level (≤23 mEq/L).

Analytical Approach

Longitudinal analyses were conducted using mixed-effects models to examine associations of BMI with serum bicarbonate levels over time and Cox proportional hazards models to examine associations of BMI with incident low bicarbonate levels.

Results

During a median follow-up of 4.4 (interquartile range, 2.3-6.3) years, patients had a median of 8 serum bicarbonate measurements and 34,539 patients developed low bicarbonate levels. Higher BMI was associated with progressively lower serum bicarbonate levels, with attenuation of the association in the highest BMI groups, suggesting a J-shaped relationship. Compared with the reference group (BMI, 18.5 to <25 kg.m²), patients with BMIs of 25 to <30, 30 to <35, 35 to <40, and ≥40 kg/m² had HRs for incident low bicarbonate levels of 1.10 (95% CI, 1.05-1.14), 1.16 (95% CI, 1.11-1.21), 1.20 (95% CI, 1.14-1.26), and 1.15 (95% CI, 1.09-1.22). Results were similar after adjustment for serum urea nitrogen level and exclusion of patients with diabetes, hypertension, or estimated glomerular filtration rates < 60 mL/min/1.73 m².

Limitations

Arterial pH measurements were unavailable.

Conclusions

Higher BMI is independently associated with progressively greater risk for developing low serum bicarbonate levels, indicating likely metabolic acidosis. Further research should explore the causes of low bicarbonate levels in patients with overweight and obesity.

The effect of body acid-base state and manipulations on body glucose regulation in human

Long-term exposure to high dietary acid load has been associated with insulin resistance and type 2 diabetes in epidemiological studies. However, it remains unclear whether the acid load of the diet translates to mild metabolic acidosis and whether it is responsible for the impairment in glucose regulation in humans. Previously, in a cross-sectional study we have reported that dietary acid load was not different between healthy individuals with normal weight and those with overweight/obesity, irrespective of insulin sensitivity. However, 4-week high acid load diet increased plasma lactate (a small component of the anion gap) and increased insulin resistance in healthy participants. The change in plasma lactate correlated significantly with the change in insulin resistance. Because cause-and-effect could not be evaluated in these settings, we sought to directly test the effect of an alkalizing treatment preload on postprandial glucose regulation. In a randomized placebo-controlled study with a crossover design, we administered sodium bicarbonate (NaHCO₃, 1.68 g) prior to high acid load meal to healthy individuals. We found that while the bicarbonate preload attenuated the post meal decrease in pH observed with placebo, no effect on postprandial glucose regulation (glucose, insulin, and C-peptide) was observed. Following 3-month treatment of nondiabetic individuals with bicarbonate, others have reported no change in insulin resistance markers, consistent with our findings. Together, studies in human suggest that insulin resistance associated with longstanding obesogenic diet may be mediated by mild metabolic acidosis. However, buffering the Western diet with bicarbonate and increasing body pH does not change glucose homeostasis in nondiabetic individuals. Further studies are required to shed light on the role of body acid-base balance and glucose homeostasis in health and disease.

Dietary acid load and cardiometabolic risk factors: a systematic review and meta-analysis of observational studies

OBJECTIVE

Dietary acid load (DAL) might contribute to change the levels of cardiometabolic risk factors; however, the results are conflicting. The present review was conducted to determine the relationship between DAL and cardiometabolic risk factors.

DESIGN

Systematic review and meta-analysis.

SETTING

A systematic search was conducted in electronic databases including ISI Web of Science, PubMed/MEDLINE, Scopus and Google Scholar for observational studies which assessed cardiometabolic risk factors across DAL. Outcomes were lipid profile, glycaemic factors and anthropometric indices. Effect sizes were derived using a fixed- or random-effect model (DerSimonian-Laird). Also, subgroup analysis was performed to find the probable source of heterogeneity. Egger's test was performed for finding any publication bias.

RESULTS

Thirty-one studies were included in the current review with overall sample size of 92 478. There was a significant relationship between systolic blood pressure (SBP; weighted mean difference (WMD) = 1·74 (95 % CI 0·25, 3·24) mmHg; P = 0·022; I2 = 95·3 %), diastolic blood pressure (DBP; WMD = 0·75 (95 % CI 0·07, 1·42) mmHg; P = 0·030; I2 = 80·8 %) and DAL in cross-sectional studies. Serum lipids, glycaemic parameters including fasting blood sugar, glycated Hb, serum insulin, homeostatic model assessment of insulin resistance and waist circumference had no significant relationship with DAL. No publication bias was found. BMI was not associated with DAL in both cross-sectional and cohort studies.

CONCLUSIONS

Higher DAL is associated with increased SBP and DBP. More studies are needed to find any relationship of DAL with lipid profile and glycaemic factors.

A Network Analysis of Biomarkers for Type 2 Diabetes

Numerous studies have investigated individual biomarkers in relation to risk of type 2 diabetes. However, few have considered the interconnectivity of these biomarkers in the etiology of diabetes as well as the potential changes in the biomarker correlation network during diabetes development. We conducted a secondary analysis of 27 plasma biomarkers representing glucose metabolism, inflammation, adipokines, endothelial dysfunction, IGF axis, and iron store plus age and BMI at blood collection from an existing case-control study nested in the Nurses' Health Study (NHS), including 1,303 incident diabetes case subjects and 1,627 healthy women. A correlation network was constructed based on pairwise Spearman correlations of the above factors that were statistically different between case and noncase subjects using permutation tests (P < 0.0005). We further evaluated the network structure separately among diabetes case subjects diagnosed <5, 5-10, and >10 years after blood collection versus noncase subjects. Although pairwise biomarker correlations tended to have similar directions comparing diabetes case subjects to noncase subjects, most correlations were stronger in noncase than in case subjects, with the largest differences observed for the insulin/HbA_1c and leptin/adiponectin correlations. Leptin and soluble leptin receptor were two hubs of the network, with large numbers of different correlations with other biomarkers in case versus noncase subjects. When examining the correlation network by timing of diabetes onset, there were more perturbations in the network for case subjects diagnosed >10 years versus <5 years after blood collection, with consistent differential correlations of insulin and HbA_1c C-peptide was the most highly connected node in the early-stage network, whereas leptin was the hub for mid- or late-stage networks. Our results suggest that perturbations of the diabetes-related biomarker network may occur decades prior to clinical recognition. In addition to the persistent dysregulation between insulin and HbA_1c, our results highlight the central role of the leptin system in diabetes development.

The Proposal of Molecular Mechanisms of Weak Organic Acids Intake-Induced Improvement of Insulin Resistance in Diabetes Mellitus via Elevation of Interstitial Fluid pH

Blood contains powerful pH-buffering molecules such as hemoglobin (Hb) and albumin, while interstitial fluids have little pH-buffering molecules. Thus, even under metabolic disorder conditions except severe cases, arterial blood pH is kept constant within the normal range (7.35~7.45), but the interstitial fluid pH under metabolic disorder conditions becomes lower than the normal level. Insulin resistance is one of the most important key factors in pathogenesis of diabetes mellitus, nevertheless the molecular mechanism of insulin resistance occurrence is still unclear. Our studies indicate that lowered interstitial fluid pH occurs in diabetes mellitus, causing insulin resistance via reduction of the binding affinity of insulin to its receptor. Therefore, the key point for improvement of insulin resistance occurring in diabetes mellitus is development of methods or techniques elevating the lowered interstitial fluid pH. Intake of weak organic acids is found to improve the insulin resistance by elevating the lowered interstitial fluid pH in diabetes mellitus. One of the molecular mechanisms of the pH elevation is that: (1) the carboxyl group (R-COO⁻) but not H⁺ composing weak organic acids in foods is absorbed into the body, and (2) the absorbed the carboxyl group (R-COO⁻) behaves as a pH buffer material, elevating the interstitial fluid pH. On the other hand, high salt intake has been suggested to cause diabetes mellitus; however, the molecular mechanism is unclear. A possible mechanism of high salt intake-caused diabetes mellitus is proposed from a viewpoint of regulation of the interstitial fluid pH: high salt intake lowers the interstitial fluid pH via high production of H⁺ associated with ATP synthesis required for the Na⁺,K⁺-ATPase to extrude the high leveled intracellular Na⁺ caused by high salt intake. This review article introduces the molecular mechanism causing the lowered interstitial fluid pH and insulin resistance in diabetes mellitus, the improvement of insulin resistance via intake of weak organic acid-containing foods, and a proposal mechanism of high salt intake-caused diabetes mellitus.

Are low levels of serum bicarbonate associated with risk of progressing to impaired fasting glucose/diabetes? A single-centre prospective cohort study in Beijing, China

AIMS

Bicarbonate is involved in many human essential metabolic processes, but little is known about the association between serum bicarbonate and glucose metabolism. This study aims to investigate the association between serum bicarbonate and the risk of progressing to impaired fasting glucose (IFG)/diabetes mellitus (DM).

SETTING

The data were obtained from a large-scale prospective cohort study in a single health centre in Beijing.

PARTICIPANTS

A total of 5318 participants aged 18-70 years who underwent health examinations annually with baseline fasting plasma glucose (FPG) ranging from 3.9 to 5.5 mmol/L, without a history of either diabetes or concomitant chronic diseases, were enrolled in this 6-year observational study.

PRIMARY OUTCOME MEASURES

A logistic regression analysis was used to calculate ORs for progressing to IFG/DM by the category of baseline serum bicarbonate. In addition, an analysis of the receiver operating characteristic (ROC) curve for predicting IFG was performed.

RESULTS

Of the 5318 participants, 210 developed IFG after a median 2.2 years of follow-up. After adjusting for sex, age, FPG, body mass index, systolic blood pressure, serum creatinine, serum alanine aminotransferase and low-density lipoprotein cholesterol at baseline, the participants in the first (OR 4.18, 95% CI 2.42 to 7.21; p<0.001), second (OR 3.02, 95% CI 1.71 to 5.33; p<0.001) and third (OR 2.12, 95% CI 1.15 to 3.89; p=0.015) quartiles of serum bicarbonate had higher odds for progressing to IFG/DM compared with those in the highest quartile. The area under the ROC curve for predicting IFG/DM was 0.69 (95% CI 0.65 to 0.72; p<0.001).

CONCLUSIONS

Lower serum bicarbonate is associated with higher risk of the development of IFG/DM.

Insulin Sensitivity and Glucose Homeostasis Can Be Influenced by Metabolic Acid Load

Recent epidemiological findings suggest that high levels of dietary acid load can affect insulin sensitivity and glucose metabolism. Consumption of high protein diets results in the over-production of metabolic acids which has been associated with the development of chronic metabolic disturbances. Mild metabolic acidosis has been shown to impair peripheral insulin action and several epidemiological findings suggest that metabolic acid load markers are associated with insulin resistance and impaired glycemic control through an interference intracellular insulin signaling pathways and translocation. In addition, higher incidence of diabetes, insulin resistance, or impaired glucose control have been found in subjects with elevated metabolic acid load markers. Hence, lowering dietary acid load may be relevant for improving glucose homeostasis and prevention of type 2 diabetes development on a long-term basis. However, limitations related to patient acid load estimation, nutritional determinants, and metabolic status considerably flaws available findings, and the lack of solid data on the background physiopathology contributes to the questionability of results. Furthermore, evidence from interventional studies is very limited and the trials carried out report no beneficial results following alkali supplementation. Available literature suggests that poor acid load control may contribute to impaired insulin sensitivity and glucose homeostasis, but it is not sufficiently supportive to fully elucidate the issue and additional well-designed studies are clearly needed.

Dietary acid load and risk of type 2 diabetes: A systematic review and dose-response meta-analysis of prospective observational studies

BACKGROUND & AIMS

Existing evidence suggests a link between acid-forming potential of diet and type 2 diabetes. But the degree of the associations and shape of the dose-response relations across different indices of diet-dependent acid load and risk of type 2 diabetes and potential confounding by sex have not been established. We aimed to test the dose-response association of different measures of dietary acid load and risk of incident type 2 diabetes, with considering the sex as a potential confounder.

METHODS

Systematic search was done using PubMed and Scopus, from inception up to September 2017. Prospective observational studies reporting the risk estimates of type 2 diabetes for three or more quantitative categories of potential renal acid load (PRAL), net endogenous acid production (NEAP) and animal protein-to-potassium ratio (A:P) scores were included. Pooled relative risks (RRs) were calculated using random effects models.

RESULTS

Seven prospective cohort studies with 319,542 participants and 17,986 incident cases of type 2 diabetes were included. Pooled RRs for a 5 unit increment in dietary PRAL, NEAP and A:P was 1.04 (95% CI: 1.01, 1.06; I² = 79%, n = 7), 1.03 (95% CI: 1.01, 1.04; I² = 54%, n = 7), and 1.11 (95% CI: 1.07, 1.15; I² = 41%, n = 3), respectively. Subgroup analysis resulted in significant positive relationship only among women, compared with men. There was a linear association between NEAP and A:P scores and risk of type 2 diabetes, whereas the association appeared to be U-shaped in analysis of PRAL.

CONCLUSIONS

Adherence to a diet with high acid-forming potential might increase the risk of type 2 diabetes. Shape of the dose-response relations across different indices of dietary acid load and potential sex differences in the associations need to be further explored. The interpretation of the results is limited by low number of studies.

Examining the Impact of Adherence to a Vegan Diet on Acid-Base Balance in Healthy Adults

Acidogenic diets, commonly measured by the potential renal acid load (PRAL), have been linked with metabolic diseases including insulin resistance, hepatic dysfunction, and cardiometabolic risk. Vegan diets are linked to low dietary acid loads, but the degree of adherence to a vegan diet to demonstrate this benefit is unknown. This study compared the change in PRAL and urine pH of omnivores who followed a vegan diet for either 2, 3, or 7 days over one week. Healthy adults were recruited from a campus population and randomly assigned to one of the three groups: VEG7 (vegan diet followed for seven consecutive days); VEG3 (vegan diet followed for three evenly spaced days over one week); or VEG2 (vegan diet followed for two evenly spaced days over one week). Gender, age, and body mass index did not differ between groups (overall: 21.8 ± 2.4 y and 24.4 ± 5.6 kg/m²). Following the one week intervention, outcome measures did not vary between the VEG2 and VEG3 groups, and these groups were collapsed for the final analyses. The 24-h urine pH was raised after seven consistent days of vegan diet adherence and was unchanged after 2-3 days of vegan diet adherence over the course of a week (+0.52 ± 0.69 and -0.02 ± 0.56 respectively, p = 0.048). However, dietary PRAL scores fell significantly in both dietary groups during the 7-day trial. Since low dietary PRAL scores have been related to improve metabolic parameters, adoption of a vegan diets for several days per week should be explored as a diet strategy to lower disease risk.

Prevention and Therapy of Type 2 Diabetes-What Is the Potential of Daily Water Intake and Its Mineral Nutrients?

We aim to present an overview of the possible influence of drinking water in general and mineral water in particular in improving glycemic parameters in persons with or without type 2 diabetes. We performed a literature search that produced 15 randomized controlled trials (RCTs) on this topic with mainly small sample sizes. We also discuss relevant observational and animal studies as well as the effects of important supplements in mineral water such as hydrogencarbonate and magnesium. There is low evidence for the positive effects of water or mineral water in improving glycemic parameters in diabetic and non-diabetic persons, and the results are heterogenous, making it difficult to reach an unequivocal conclusion. Meta-analyses of prospective cohort studies and other observational studies, studies with animal models and interventional studies using hydrogencarbonate and magnesium supplements suggest a probable positive effect of drinking water and mineral water in particular on glycemic parameters, supporting the positive results found in some of the RCTs, especially those substituting diet beverages or caloric beverages with water, or those using bicarbonate and magnesium-rich water. Regarding the high prevalence, the associated suffering and the resulting health expenditures of type 2 diabetes, it is imperative to conduct larger and more rigorous trials to answer the question whether drinking water or mineral water can improve glycemic parameters in diabetic and non-diabetic persons.

The Effect of Buffering High Acid Load Meal with Sodium Bicarbonate on Postprandial Glucose Metabolism in Humans-A Randomized Placebo-Controlled Study

Background: High dietary acid load relates to increased risk of type 2 diabetes in epidemiological studies. We aimed to investigate whether buffering a high acid load meal with an alkalizing treatment changes glucose metabolism post meal. Methods: Non-diabetic participants (n = 32) were randomized to receive either 1680 mg NaHCO₃ or placebo, followed by a high acid load meal in a double-blind placebo-controlled crossover (1–4 weeks apart) study. Thirty (20 men) participants completed the study. Venous blood pH, serum bicarbonate, blood glucose, serum insulin, C-peptide, non-esterified fatty acid (NEFA), and plasma glucagon-like peptide-1 (GLP-1) concentrations were measured at baseline (fasting) and at 15–30 min intervals for 3 h post meal. Results: The treatment was well tolerated. Venous blood pH declined in the first 15 min post meal with the placebo (p = 0.001), but not with NaHCO₃ (p = 0.86) and remained decreased with the placebo for 3 h (p_interaction = 0.04). On average over the 3 h blood pH iAUC was greater with NaHCO₃ compared with placebo (p = 0.02). However, postprandial glucose, insulin, C-peptide, NEFA and GLP-1 were not different between treatments (p_interaction ≥ 0.07). Conclusions: An alkalizing medication administered pre-meal has no acute effect on glycaemia and insulin response in healthy individuals. Long-term interventions in at-risk populations are necessary to investigate the effect of sustained alkalization on glucose metabolism.

Urinary pH is a predictor of diabetes in men; a population based large scale cohort study

AIMS

Previous cross-sectional studies revealed that patients with type 2 diabetes were associated with low urine pH. However, the association between urinary pH and incident type 2 diabetes is still unclear. Thus, we investigated the association between urinary pH and incident type 2 diabetes.

METHODS

This is a 5-year observational study of 3119men. We divided participants into four groups according to quartile of urinary pH. Multivariate logistic regression analysis was performed to calculate adjusted odds ratios (ORs) and 95% CIs for incident type 2 diabetes. We adjusted for age, body mass index, smoking, exercise, alcohol consumption, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol levels and impaired fasting glycaemia.

RESULTS

In the follow-up examination, 113men diagnosed as diabetes. The proportion of incident diabetes was 6.9% (case/N=22/318) in the lowest urinary pH group (urinary pH = 5.0), 3.4% (46/1366) in the second lowest group (urinary pH = 5.5), 3.5% (30/856) in the third lowest group (urinary pH = 6.0) and 2.6% (15/579) in the highest group (urinary pH≥6.5). The lowest urinary pH group was associated with the increased risk of incident diabetes compared to the other urinary pH groups (multivariate OR=1.91, 95% CI 1.05-3.36, p=0.033 for the second lowest, multivariate OR=1.99, 95% CI 1.05-3.71, p=0.036 for the third lowest and multivariate OR 2.69, 95% CI 1.30-5.72, p=0.008 for the highest urinary pH groups).

CONCLUSIONS

Low urine pH is an independent predictor of diabetes. We suggest that the urine pH can be an easy practical marker for diabetes.

Diet-Induced Low-Grade Metabolic Acidosis and Clinical Outcomes: A Review

Low-grade metabolic acidosis is a condition characterized by a slight decrease in blood pH, within the range considered normal, and feeding is one of the main factors that may influence the occurrence of such a condition. The excessive consumption of acid precursor foods (sources of phosphorus and proteins), to the detriment of those precursors of bases (sources of potassium, calcium, and magnesium), leads to acid-base balance volubility. If this condition occurs in a prolonged, chronic way, low-grade metabolic acidosis can become significant and predispose to metabolic imbalances such as kidney stone formation, increased bone resorption, reduced bone mineral density, and the loss of muscle mass, as well as the increased risk of chronic diseases such as type 2 diabetes mellitus, hypertension, and non-alcoholic hepatic steatosis. Considering the increase in the number of studies investigating the influence of diet-induced metabolic acidosis on clinical outcomes, this review gathers the available evidence evaluating the association of this disturbance and metabolic imbalances, as well as related mechanisms. It is necessary to look at the western dietary pattern of most countries and the increasing incidence of non-comunicable diseases for the balance between fruit and vegetable intake and the appropriate supply of protein, mainly from animal sources, so that it does not exceed the daily recommendations.

Role of Acid-Base Homeostasis in Diabetic Kidney Disease

PURPOSE OF REVIEW

Acid-base homeostasis is impaired in chronic kidney disease (CKD) and may contribute to disease progression. Diabetes, a major cause of CKD worldwide, may exacerbate acidosis further due to differences in acid production and excretion. Here, we review the role of abnormal acid-base homeostasis in the pathogenesis and progression of diabetes and diabetic kidney disease.

RECENT FINDINGS

Acidosis and dietary acid loading may contribute to the development and worsening of insulin resistance and hypertension, thereby promoting diabetes and diabetic CKD. However, although metabolic acidosis associates with progression of CKD generally, the results in diabetic CKD are mixed. Data suggests that metabolic acid production in diabetes may be higher than would be predicted based on dietary intake alone, and new observational data suggests that this higher diet-independent acid production could potentially be protective. The role of acid-base homeostasis in diabetic CKD progression is complex and must consider differences in endogenous acid production and excretion in diabetes. Ongoing observational and interventional studies in this field should consider the unique physiology of diabetes.

Diet-dependent acid load and type 2 diabetes: pooled results from three prospective cohort studies

AIMS/HYPOTHESIS

Studies suggest a potential link between low-grade metabolic acidosis and type 2 diabetes. A western dietary pattern increases daily acid load but the association between diet-dependent acid load and type 2 diabetes is still unclear. This study aimed to assess whether diet-dependent acid load is associated with the risk of type 2 diabetes.

METHODS

We examined the association between energy-adjusted net endogenous acid production (NEAP), potential renal acid load (PRAL) and animal protein-to-potassium ratio (A:P) on incident type 2 diabetes in 67,433 women from the Nurses' Health Study, 84,310 women from the Nurses' Health Study II and 35,743 men from the Health Professionals' Follow-up Study who were free from type 2 diabetes, cardiovascular disease and cancer at baseline. Study-specific HRs were estimated using Cox proportional hazards models with time-varying covariates and were pooled using a random effects meta-analysis.

RESULTS

We documented 15,305 cases of type 2 diabetes during 4,025,131 person-years of follow-up. After adjustment for diabetes risk factors, dietary NEAP, PRAL and A:P were positively associated with type 2 diabetes (pooled HR [95% CI] for highest (Q5) vs lowest quintile (Q1): 1.29 [1.22, 1.37], p _trend <0.0001; 1.29 [1.22, 1.36], p _trend <0.0001 and 1.32 [1.24, 1.40], p _trend <0.0001 for NEAP, PRAL and A:P, respectively). These results were not fully explained by other dietary factors including glycaemic load and dietary quality (HR [95% CI] for Q5 vs Q1: 1.21 [1.09, 1.33], p _trend <0.0001; 1.19 [1.08, 1.30] and 1.26 [1.17, 1.36], p _trend <0.0001 for NEAP, PRAL and A:P, respectively).

CONCLUSIONS/INTERPRETATION

This study suggests that higher diet-dependent acid load is associated with an increased risk of type 2 diabetes. This association is not fully explained by diabetes risk factors and overall diet quality.

Serum Bicarbonate Is Associated with Heart Failure in the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Low serum bicarbonate concentrations are associated with mortality and kidney disease progression. Data regarding associations between bicarbonate and cardiovascular disease (CVD) are scarce.

METHODS

We performed a cohort study of 6,229 adult participants from the Multi-Ethnic Study of Atherosclerosis, a community-based cohort free of CVD at baseline. Serum bicarbonate was measured at baseline. Cardiovascular outcomes were defined as: (1) subclinical CVD (left ventricular mass [LVM] and aortic pulse pressure [PP] measured at baseline), (2) incident atherosclerotic cardiovascular events (CVE; composite of myocardial infarction, resuscitated cardiac arrest, stroke, coronary heart disease death, and stroke death), and (3) incident heart failure.

RESULTS

During a median (interquartile range) follow-up of 8.5 (7.7-8.6) years, 331 (5.3%) participants had an incident CVE and 174 (2.8%) developed incident heart failure. We stratified analyses by use of diuretics because we observed a significant interaction between diuretic use and bicarbonate with study outcomes. Among diuretic nonusers, with adjustment, bicarbonate ≥25 mEq/L was associated with an estimated 3.0 g greater LVM (95% CI 0.5-5.0) and 1.0 mm Hg higher aortic PP (95% CI 0.4-2.0) compared to bicarbonate 23-24 mEq/L. Each 1 mEq/L of bicarbonate increase was associated with a 13% higher risk of incident heart failure (hazards ratio 1.13, 95% CI 1.01-2.11). Among diuretic users, higher bicarbonate was not associated with CVD. Bicarbonate was not associated with incident atherosclerotic CVE irrespective of diuretic use.

CONCLUSION

Among nonusers of diuretics in a large community-based study, higher serum bicarbonate concentrations are associated with subclinical CVD and new heart failure.

Correction of metabolic acidosis improves insulin resistance in chronic kidney disease

Background

Correction of metabolic acidosis (MA) with nutritional therapy or bicarbonate administration is widely used in chronic kidney disease (CKD) patients. However, it is unknown whether these interventions reduce insulin resistance (IR) in diabetic patients with CKD. We sought to evaluate the effect of MA correction on endogenous insulin action in diabetic type 2 (DM2) CKD patients.

Methods

A total of 145 CKD subjects (83 men e 62 women) with DM2 treated with oral antidiabetic drugs were included in the study and followed up to 1 year. All patients were randomly assigned 1:1 to either open-label (A) oral bicarbonate to achieve serum bicarbonate levels of 24–28 mmol/L (treatment group) or (B) no treatment (control group). The Homeostatic model assessment (HOMA) index was used to evaluate IR at study inception and conclusion. Parametric and non-parametric tests as well as linear regression were used.

Results

At baseline no differences in demographic and clinical characteristics between the two groups was observed. Average dose of bicarbonate in the treatment group was 0.7 ± 0.2 mmol/kg. Treated patients showed a better metabolic control as confirmed by lower insulin levels (13.4 ± 5.2 vs 19.9 ± 6.3; for treated and control subjects respectively; p < 0.001), Homa-IR (5.9[5.0-7.0] vs 6.3[5.3–8.2]; p = 0.01) and need for oral antidiabetic drugs. The serum bicarbonate and HOMA-IR relationship was non-linear and the largest HOMA-IR reduction was noted for serum bicarbonate levels between 24 and 28 mmol/l. Adjustment for confounders, suggests that serum bicarbonate rather than treatment drives the effect on HOMA-IR.

Conclusions

Serum bicarbonate is related to IR and the largest HOMA-IR reduction is noted for serum bicarbonate between 24 and 28 mmol/l. Treatment with bicarbonate influences IR. However, changes in serum bicarbonate explains the effect of treatment on HOMA index. Future efforts are required to validate these results in diabetic and non-diabetic CKD patients.

Trial registration

The trial was registered at www.clinicaltrial.gov (Use of Bicarbonate in Chronic Renal Insufficiency (UBI) study - NCT01640119)

Modest U-Shaped Association between Dietary Acid Load and Risk of All-Cause and Cardiovascular Mortality in Adults

BACKGROUND

Conflicting evidence associates diet acidity with the incidence of chronic diseases such as hypertension, diabetes, kidney disease, and bone-mineral disorders. It is currently unknown whether dietary acidity is associated with death.

OBJECTIVE

We investigated the association of dietary acid load with the risk of all-cause and cardiovascular disease (CVD) mortality.

METHODS

We used data from 2 prospective cohorts, the Swedish Mammography Cohort and the Cohort of Swedish Men, which included 36,740 women and 44,957 men aged 45-84 y at the start of a 15-y follow-up period (1998-2012). Acid load was estimated from food-frequency questionnaires by use of the validated potential renal acid load (PRAL) algorithm. Deaths were ascertained via record linkage. Associations of PRAL with mortality were modeled by use of restricted cubic splines.

RESULTS

The median PRAL was 0.65 mEq/d (range: -109 to 81.5 mEq/d) in women and 12.3 mEq/d (-111 to 121 mEq/d) in men. During a mean of 13.5 ± 3.3 y of follow-up, there were 8576 and 13,332 deaths, of which 3203 and 5427 were attributed to cardiovascular causes in woman and men, respectively. In both sexes, a nonlinear U-shaped relation was observed, with higher mortality rates for both dietary acid and alkali excess. Compared with neutral PRAL (0 mEq/d), the HRs for all-cause mortality for the 10th and 90th percentiles of PRAL were 1.05 (95% CI: 1.01, 1.10) and 1.03 (95% CI: 0.98, 1.08), respectively, in women. The corresponding results for men were HRs 1.01 (95% CI: 1.00, 1.02) and 1.04 (95% CI: 1.00, 1.08) respectively. This relation was slightly stronger for CVD mortality.

CONCLUSIONS

Excess diet alkalinity and acidity both showed weak associations with higher mortality in Swedish adults. An acid-base balanced diet was associated with the lowest mortality, but the magnitude of mortality reduction was modest. The Swedish Mammography Cohort was registered at clinicaltrials.gov as NCT01127698 The Cohort of Swedish Men was registered at clinicaltrials.gov as NCT01127711.

Effects of potassium citrate or potassium chloride in patients with combined glucose intolerance: A placebo-controlled pilot study

BACKGROUND

Experimental K(+) depletion reversibly inhibits insulin secretion, while chronic metabolic acidosis decreases insulin sensitivity. We aimed to investigate the effects of potassium supplementation and alkali supplementation in non-acidotic, normokalemic humans with combined glucose intolerance.

STUDY DESIGN AND RESULTS

In this double-blind, placebo-controlled study in 11 subjects (7 male, 4 female, ages 47-63 years), 90meqs of oral KCl or Kcitrate per day for 2weeks each increased insulin production as measured by homeostasis model assessment Beta [KCl=86 (CI 81-91), Kcitrate=88 (82-94), placebo=78 (73-83)%, p<0.04], but only Kcitrate attenuated insulin resistance as assessed by HOMA-IR (insulin resistance, Kcitrate=2.8 (2.5-3.1), placebo=3.2 (2.9-3.5), p<0.03) and only Kcitrate increased quantitative insulin sensitivity check index (Quicki, Kcitrate=0.355 (0.305-0.405), placebo=0.320 (0.265-0.375) p<0.04). These results were confirmed by independent measurements, i.e. HOMA C-peptide and whole body insulin sensitivity index measured during oral glucose tolerance testing. Kcitrate significantly decreased systolic and diastolic 24-hour ambulatory blood pressures (-4.0 (-3 to -5) and -2.7 (-1.9 to -3.5), respectively as compared to placebo, p<0.02) while KCl was without a significant effect.

CONCLUSIONS

K(+) supplementation in the absence of overt K(+) depletion improves beta-cell function in subjects with combined glucose intolerance. The insulin-sensitizing and hypotensive effect, however, depend on citrate as the accompanying anion.

CKD-Mineral Bone Disorder in Stage 4 and 5 CKD: What We Know Today?

Patients with CKD stages 4 and 5 experience biochemical derangements associated with CKD-mineral bone disorder. Some of the key abnormalities are hyperparathyroidism, hyperphosphatemia, hypocalcemia, and metabolic acidosis. We review the available treatments for these conditions and the evidence behind the treatments. We conclude that there is greater evidence for treating hyperphosphatemia than hyperparathyroidism. Treatment of metabolic acidosis in small clinical trials appears to be safe. We caution the reader about side effects associated with some of these treatments that differ in patients with CKD Stages 4 and 5 compared with patients on dialysis. The use of cinacalcet has been associated with hyperphosphatemia in patients with functioning kidneys. Activated vitamin D therapy has been associated with elevated creatinine levels, which may or may not be a reflection of true decrement in kidney function. Finally, the use of non-calcium-containing phosphate binders may be associated with improved clinical outcomes in patients; however, many more clinical trials are needed in this important area of medicine.

High Dietary Acid Load Score Is Associated with Increased Risk of Type 2 Diabetes in Japanese Men: The Japan Public Health Center-based Prospective Study

BACKGROUND

Diet-induced metabolic acidosis has been linked to cardiometabolic abnormalities in Westerners, but the evidence on this issue is scarce in Asians.

OBJECTIVE

The present study prospectively examined the association between dietary acid load and type 2 diabetes (T2D) in Japanese adults.

METHODS

Study participants were 27,809 men and 36,851 women, aged 45-75 y, who completed a dietary questionnaire of the second survey of the Japan Public Health Center-based Prospective Study and had no previous history of T2D. Dietary intake was assessed by using a validated 147-item food-frequency questionnaire. Potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores were derived from the nutrient intake. A multilevel logistic regression model was used to estimate ORs and 95% CIs of self-reported, physician-diagnosed T2D over 5 y, with adjustment for potential confounding variables.

RESULTS

A total of 1191 cases of newly diagnosed T2D were reported. PRAL score was positively associated with T2D in men; the multivariable-adjusted ORs (95% CIs) for the lowest through the highest quartiles of PRAL were 1.00, 1.09 (0.87, 1.36), 1.10 (0.88, 1.37), and 1.25 (1.01, 1.55) (P-trend = 0.047). Further adjustment for dietary intake strengthened the association. NEAP score was not associated with the risk of T2D (P-trend = 0.20). In stratified analyses, the positive association between PRAL and T2D was confined to younger men (age <50 y; P-trend = 0.046). There was no association between dietary acid load score and T2D in women.

CONCLUSION

A high dietary acid load score is associated with an increased risk of T2D in Japanese men.

Dietary Acid Load is Associated With Serum Bicarbonate but not Insulin Sensitivity in Chronic Kidney Disease

OBJECTIVE

In chronic kidney disease (CKD), dietary acid may promote metabolic acidosis and insulin resistance, which in turn may contribute to adverse clinical health outcomes. We examined associations between dietary acid load, serum bicarbonate, and insulin sensitivity in CKD.

DESIGN

In a cross-sectional study, we collected 3-day prospective food diaries to quantify dietary acid load as net endogenous acid production (NEAP, the nonvolatile acid load produced by the diet's acid balance) and potential renal acid load (PRAL). We measured urine net acid excretion (NAE) in 24-hour urine samples. Insulin sensitivity was measured by hyperinsulinemic euglycemic clamp.

SUBJECTS

Forty-two patients with CKD Stages 3 to 5 attending nephrology clinics in the Pacific Northwest and 21 control subjects (estimated glomerular filtration rate [eGFR] ≥ 60 mL/minute/1.73 m(2)).

MAIN OUTCOME MEASURES

Serum bicarbonate and insulin sensitivity (SIclamp).

RESULTS

Mean age was 60.8 ± 13.6 years, and 54% of participants were men. Mean eGFR and serum bicarbonate concentrations were 34.4 ± 13.1 mL/minute/1.73 m(2) and 24.1 ± 2.9 mEq/L for participants with CKD and 88.6 ± 14.5 mL/minute/1.73 m(2) and 26.3 ± 1.8 mEq/L for control subjects, respectively. Mean NEAP, PRAL, and NAE were 58.2 ± 24.3, 9.7 ± 18.4, and 32.1 ± 19.8 mEq/day, respectively. Considering all participants, dietary acid load was significantly, inversely associated with serum bicarbonate, adjusting for age, gender, race, eGFR, body mass index, and diuretic use: -1.2 mEq/L per standard deviation (SD) NEAP (95% confidence interval [CI] -1.8 to -0.6, P < .0001); -0.9 mEq/L bicarbonate per SD PRAL (95% CI -1.5 to -0.4, P = .0005); -0.7 mEq/L bicarbonate per SD NAE (95% CI -1.2 to -0.1, P = .01). These associations were similar in participants with and without CKD. However, neither NEAP and PRAL nor NAE was significantly associated with SIclamp. Serum bicarbonate was also not significantly associated with SIclamp.

CONCLUSIONS

In CKD, dietary acid load is associated with serum bicarbonate, suggesting that acidosis may be improved by dietary changes, but not with insulin sensitivity.

Association between lower serum bicarbonate and renal hyperfiltration in the general population with preserved renal function: a cross-sectional study

Background

Lower serum bicarbonate, mainly due to the modern Western-style diet, and renal hyperfiltration (RHF) are both independently associated with higher mortality in the general population with preserved renal function. The objective of this study was to evaluate the association between serum bicarbonate and RHF.

Methods

The health data of 41,886 adults with an estimated glomerular filtration rate (eGFR) ≥60 mL/min per 1.73 m² were analyzed. The eGFR was calculated with the Chronic Kidney Disease Epidemiology Collaboration creatinine equation and RHF was defined as eGFR with adjusted residuals > sex-specific 95^th percentile.

Results

The adjusted mean of eGFR was lower in the highest quintile of serum bicarbonate than in other quintiles, after adjusting for confounders. A lower percentile rank of serum bicarbonate was associated with higher odds of RHF. The odds ratio (OR) for RHF in the lowest quintile of serum bicarbonate was 1.39 (95 % confidence interval, 95 % CI, 1.11–1.75) compared to the highest, after adjusting for confounders. With subgroup analysis, the association was prominent in participants with a body mass index >25 kg/m² (OR 1.98, 95 % CI 1.32–2.95 in the lowest quintile compared to the highest), compared to those with a body mass index ≤25 kg/m² (OR 1.18, 95 % CI 0.89–1.56 in the lowest quintile compared to the highest).

Conclusions

This study observed an association between lower serum bicarbonate and higher odds of RHF and the possible differential effect of obesity in this association. It is necessary to confirm the association between lower serum bicarbonate and RHF and its causality.

Association between the markers of metabolic acid load and higher all-cause and cardiovascular mortality in a general population with preserved renal function

Although metabolic acid load has been associated with many well-known risk factors for mortality, its clinical implications are not yet clear. To evaluate the association between biomarkers of metabolic acid load, such as serum bicarbonate, serum anion gap and urine pH and mortality, we analyzed the health records of 31,590 adults who underwent a health screening between January 2001 and December 2010 and had an estimated glomerular filtration rate ⩾60 ml min(-1) per 1.73 m2. Urine pH was measured by a dipstick test performed on fast morning urine sample and categorized as acidic (urine pH ⩽5.5), neutral and alkaline (urine pH ⩾8.0). Using the Cox proportional hazard model, the adjusted hazard ratio (aHR) of all-cause mortality of the lowest quartile of serum bicarbonate was 1.460 (95% confidence interval (CI) 1.068-1.995) compared with the highest quartile, after a median follow-up of 93 months. The aHRs of cardiovascular and cancer mortality of the lowest quartile of serum bicarbonate were 2.647 (95% CI 1.148-6.103) and 1.604 (95% CI 1.024-2.513), respectively, compared with the highest quartile. Acidic and neutral urine pH were significantly associated with a higher all-cause mortality (aHR 2.550, 95% CI 1.316-4.935; aHR 2.376 95% CI 1.254-4.501, respectively), compared with an alkaline urine pH. In conclusion, higher metabolic acid load was associated with an increased all-cause and cardiovascular mortality in a healthy population. The association between metabolic acid load and mortality and the causality of the relationship need to be confirmed.

Roles of interstitial fluid pH in diabetes mellitus: Glycolysis and mitochondrial function

The pH of body fluids is one the most important key factors regulating various cell function such as enzyme activity and protein-protein interaction via modification of its binding affinity. Therefore, to keep cell function normal, the pH of body fluids is maintained constant by various systems. Insulin resistance is one of the most important, serious factors making the body condition worse in diabetes mellitus. I have recently found that the pH of body (interstitial) fluids is lower in diabetes mellitus than that in non-diabetic control, and that the lowered pH is one of the causes producing insulin resistance. In this review article, I introduce importance of body (interstitial) fluid pH in regulation of body function, evidence on abnormal regulation of body fluid pH in diabetes mellitus, and relationship between the body fluid pH and insulin resistance. Further, this review proposes perspective therapies on the basis of regulation of body fluid pH including propolis (honeybee product) diet.

Diet, lifestyle, and genetic risk factors for type 2 diabetes: a review from the Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study

The epidemiological evidence collected from three large US cohorts (Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study) has yielded important information regarding the roles of overall diet, individual foods and nutrients, physical activity and other lifestyle factors in the development of type 2 diabetes. Excess adiposity is a major risk factor for diabetes, and thus, maintaining a healthy body weight and avoidance of weight gain during adulthood is the cornerstone of diabetes prevention. Independent of body weight, the quality or type of dietary fat and carbohydrate is more crucial than the quantity in determining diabetes risk. Higher consumption of coffee, whole grains, fruits, and nuts is associated with lower risk of diabetes, whereas regular consumption of refined grains, red and processed meats, and sugar-sweetened beverages including fruits juices is associated with increased risk. Dietary patterns rich in fruits and vegetables, whole grains, and nuts and legumes but lower in red and processed meats, refined grains, and sugar-sweetened beverages are consistently associated with diabetes risk, even after adjustment for body mass index. The genome-wide association studies conducted in these cohorts have contributed substantially to the discoveries of novel genetic loci for type 2 diabetes and other metabolic traits, although the identified common variants explain only a small proportion of overall diabetes predisposition. Taken together, these ongoing large cohort studies have provided convincing epidemiologic evidence that a healthy diet, together with regular physical activity, maintenance of a healthy weight, moderate alcohol consumption, and avoidance of sedentary behaviors and smoking would prevent the majority of type 2 diabetes cases.

Dietary acid load and risk of type 2 diabetes: the E3N-EPIC cohort study

AIMS/HYPOTHESIS

The objective of this study was to evaluate the prospective relationship between dietary acid load, assessed with both the potential renal acid load (PRAL) and the net endogenous acid production (NEAP) scores, and type 2 diabetes risk.

METHODS

A total of 66,485 women from the E3N-EPIC cohort were followed for incident diabetes over 14 years. PRAL and NEAP scores were derived from nutrient intakes. HRs for type 2 diabetes risk across quartiles of the baseline PRAL and NEAP scores were estimated with multivariate Cox regression models.

RESULTS

During follow-up, 1,372 cases of incident type 2 diabetes were validated. In the overall population, the highest PRAL quartile, reflecting a greater acid-forming potential, was associated with a significant increase in type 2 diabetes risk, compared with the first quartile (HR 1.56, 95% CI 1.29, 1.90). The association was stronger among women with BMI <25 kg/m2 (HR 1.96, 95% CI 1.43, 2.69) than in overweight women (HR 1.28, 95% CI 1.00, 1.64); statistically significant trends in risk across quartiles were observed in both groups (p trend < 0.0001 and p trend = 0.03, respectively). The NEAP score provided similar findings.

CONCLUSIONS/INTERPRETATION

We have demonstrated for the first time in a large prospective study that dietary acid load was positively associated with type 2 diabetes risk, independently of other known risk factors for diabetes. Our results need to be validated in other populations, and may lead to promotion of diets with a low acid load for the prevention of diabetes. Further research is required on the underlying mechanisms.

Plasma bicarbonate and odds of incident hypertension

BACKGROUND

Several biomarkers of metabolic acidosis, including lower plasma bicarbonate, have been associated with prevalent hypertension in cross-sectional studies. We sought to examine prospectively whether lower plasma bicarbonate is associated with incident hypertension.

METHODS

We conducted a prospective case-control study nested within the Nurses' Health Study II. Plasma bicarbonate was measured in 695 nonobese women without hypertension at time of blood draw who subsequently developed hypertension during 6 years of follow-up. Control subjects were matched to case subjects according to age, race, time and day of blood draw, and day of menstrual cycle. We used unconditional logistic regression to generate odds ratios (ORs) for development of hypertension by quintile of baseline plasma bicarbonate.

RESULTS

After adjusting for matching factors, body mass index, family history of hypertension, plasma creatinine, and dietary and lifestyle factors, higher plasma bicarbonate was associated with lower odds of developing hypertension across quintiles (P for linear trend = 0.04). Those in the highest compared with the lowest quintile of plasma bicarbonate had 31% lower odds of developing hypertension (OR = 0.69; 95% confidence interval = 0.48-0.99). Further adjustment for diet-estimated net endogenous acid production, plasma insulin, 25-hydroxyvitamin D, and uric acid did not alter these findings.

CONCLUSIONS

Our case-control study is consistent with a modest association between higher plasma bicarbonate and reduced odds of developing hypertension among nonobese women, although our findings are of borderline statistical significance. Further research is required to confirm this finding as part of a larger prospective cohort study and to elucidate the mechanism for this relation.

Longitudinal relationships between diet-dependent renal acid load and blood pressure development in healthy children

Diets high in sulfur-rich protein and low in fruits and vegetables affect human acid-base balance adversely. Corresponding subclinical forms of metabolic acidosis have been linked to hypertension in adults. We longitudinally examined relations of dietary acid load with blood pressure in 257 healthy prepuberty children with 3 or more parallel 3-day weighed dietary records, 24-h urine, and blood pressure measurements. Urinary net acid excretion and the potential renal acid load (PRAL), determined as the difference of major urinary nonbicarbonate anions and mineral cations, were used to predict dietary acid load. PRAL was also calculated from dietary data. In repeated-measures regression analyses, adjusted for body size and dietary fiber, an intraindividual increase of 10 mEq above the 'usual' net acid excretion or urine PRAL were each significantly related to a 0.6-0.7 mm Hg increased systolic blood pressure. Differences in urine PRAL among the children also significantly predicted between-person differences in systolic blood pressure. A higher individual net acid excretion or urine PRAL and intraindividual increase in urine PRAL were significantly related to higher diastolic blood pressure. Blood pressure associations were nonsignificant for dietary PRAL and urinary sodium. Thus, in healthy children, renal biomarker analyses reveal an association of proton load with higher blood pressure. Especially for systolic blood pressure, a more alkalizing nutrition may be beneficial for blood pressure development within a given individual. Experimental confirmation of a causal acid load-blood pressure link is required.

The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters

The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.