Effects of dietary protein restriction on albumin and fibrinogen synthesis in macroalbuminuric type 2 diabetic patients

Effect of dietary protein intake on cognitive function in the elderly with chronic kidney disease: analysis of the National Health and Nutrition Examination Survey 2011-2014

BACKGROUND

Cognitive dysfunction is prevalent among the elderly diagnosed with chronic kidney disease (CKD). Low protein diets are used for retarding the progression of CKD in clinical practice. Nonetheless, the impact of dietary protein consumption on cognitive function in this population remains uncertain.

METHODS

We recruited 2306 participants (≥60 years) from 2011 to 2014 National Health and Nutrition Examination Survey (NHANES). 24-h dietary recall questionnaire was utilized to evaluate protein intake. Cognitive function was measured using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). Participants' characteristics were analyzed, and the interaction between protein consumption and CKD on cognitive impairment were analyzed using a logistic regression model.

RESULTS

We divided participants into three groups based on CKD stages: no CKD, CKD stage G1 to G2 (19%), and CKD stage G3 to G5 (18%). The average protein intake was 0.97 g/(kg·d). In the higher protein intake group, CKD stages G1 to G2 elevated the risk of immediate memory impairment (OR: 2.441, 95% Cl: 1.161-5.132 for protein consumption in 1.0-1.2g/(kg·d); OR: 2.225, 95% Cl: 1.015-4.876 for protein consumption in >1.2 g/(kg·d)). However, no similar resuts were observed in the lower protein intake group. In addition, the interaction between CKD status and protein intake on immediate memory was statistically significant (p = .041).

CONCLUSION

A higher probability of cognitive impairment in the elderly with early-stage CKD may be linked to higher protein intake. Low protein diets may be a potential strategy to release cognitive impairment in the elderly with early-stage CKD.

Accelerated whole-body protein catabolism in subjects with type 2 Diabetes Mellitus and albuminuria

Background

Albuminuria develops in ~40% of subjects with Type 2 Diabetes Mellitus (T2DM), and is often associated with malnutrition, severe comorbidities and decreased life expectancy. The association between albuminuria and altered whole body protein turnover in T2DM is currently unknown.

Objective

To assess whole body protein degradation and synthesis in type 2 diabetes with and without albuminuria.

Methods

Fourteen T2DM male subjects, with either increased [AER+] or normal [AER-] urinary albumin excretion rate, and eleven age-matched male healthy controls, were infused with phenylalanine [Phe] and tyrosine [Tyr] tracers. Post-absorptive rates of appearance (Ra) of Phe (= protein degradation) and Tyr, Phe hydroxylation to Tyr (Hy) (catabolic pathway), and Phe disposal to protein synthesis [PS], were determined.

Results

Phe and Tyr Ra were not different among the groups. However, in T2DM [AER+], the fraction of Phe disposal to hydroxylation was ~50% and ~25% greater than that of both controls and T2DM [AER-] (p<0.006 and p = 0.17, respectively). Conversely, as compared to controls, the fractional Phe disposal to PS was ~10% lower in T2DM [AER+] (p<0.006), and not different from that in T2DM [AER-]. As a consequence, in T2DM [AER+], the ratio between the fractional Phe disposal to hydroxylation and that to PS was ~70% greater (p = 0.005) than that in healthy controls, whereas in the T2DM [AER-] this ratio was ~30% greater than in controls (p = 0.19).

Conclusions

On the basis of the kinetics of the essential amino acid phenylalanine, T2DM subjects with increased AER exhibit a catabolic pattern of whole body protein turnover.

The Role for Protein Restriction in Addition to Renin-Angiotensin-Aldosterone System Inhibitors in the Management of CKD

In experimental studies a low-protein diet (LPD) and renin-angiotensin-aldosterone system (RAAS) inhibitors are both reported to slow the progression of chronic kidney disease (CKD) and reduce proteinuria. RAAS activity contributes to increased blood pressure, fluid retention, and positive sodium balance, but also to kidney damage by enhancing glomerular capillary filtration pressure and synthesis of profibrotic molecules such as transforming growth factor β. It has been well established that an LPD decreases glomerular hyperfiltration and the generation of uremic toxins, as well as the burden of acid load, phosphorus, and sodium. In different animal CKD models, a significant reduction in proteinuria and glomerulosclerosis has been achieved when an RAAS inhibitor and LPD were combined. To date, high-quality intervention trials investigating this combined strategy are lacking. We summarize the experimental and clinical studies that have examined a potential additive action of these therapies on CKD progression. We outline potential mechanisms of action and additive efficacy of an LPD and RAAS inhibitors in CKD, with a particular emphasis on phosphate levels, uremic toxin production, acid load, and salt intake. Finally, although the evidence is inadequate to recommend combining RAAS inhibitors and an LPD to slow the progression of CKD, we provide a perspective to support a large-scale randomized clinical trial to study this combination.

The effects of protein intake on albuminuria in different estimated glomerular filtration rate: A population-based study

BACKGROUND

Chronic kidney disease (CKD) is a serious condition associated with early mortality, decreased quality of life, and increased health-care expenditures.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) collected from 1999 to 2012 were used. Subjects were divided into 4 estimated glomerular filtration rate (eGFR) categories: stage 1: eGFR≥90mL/min/1.73m², stage 2: eGFR 60-89, stage 3: eGFR 30-59, and stage 4/5: eGFR<30, and 3 age strata (<45y, 45-64, 65+). Associations between protein intake and albuminuria were determined.

RESULTS

A total of 45,259 subjects were included. Despite decreasing protein intake, there was a significant increase in the prevalence of albuminuria with decreasing levels of eGFR. Multivariable analysis showed that albuminuria was associated with daily protein intake in patients ≥65years old with stage 1 disease, and that diabetes was associated with albuminuria in patients ≥65years old with stage 2 and 3 diseases. Overall, albuminuria in patients with stage 1 disease was associated with hours of sitting per day and blood glucose level.

CONCLUSION

Albuminuria was associated with daily protein intake in patients of 45-64years old with stage 1 CKD disease, and was associated with hours of sitting per day and blood glucose level. These data further support the importance of lifestyle changes in the management of CKD, especially in patients with early-stage disease.

Repeated quantitative measurements of De Novo synthesis of albumin and fibrinogen

The possibility of using two different isotopomers, for the incorporation of isotopically labeled amino acids, was explored to enable longitudinal studies of de novo synthesis of two export liver proteins, albumin and fibrinogen. The agreement of the synthesis rates between the two different labels was evaluated along with the reproducibility of repeated experiments using different time intervals. Healthy volunteers were studied in a standardized fed state. Protocol A (n = 10) involved two measurements 48 hours apart. Protocol B (n = 6) involved three measurements at baseline and five hours and then seven days after the initial measurement. De novo synthesis of albumin and fibrinogen by the incorporation of D5-phenylalanine or D8-phenylalanine were measured using the flooding dose technique. Albumin and fibrinogen were isolated from plasma using standard techniques. Fractional and absolute synthesis rates were calculated. Repeated measurements employing the two isotoptomers showed good agreement for albumin fractional synthesis rate after 48 hours (p = 0.92) and after 7 days (p = 0.99), with a coefficient of variation of 5.9% when using the same isotopic label. For fibrinogen, the coefficient of variation for the fractional synthesis rate employing the same isotopic label was 16.6%. Repeated measurements after 48 hours and seven days showed less agreement although there was no statistical difference (P = 0.32 and P = 0.30 respectively). Repeated measurement after five hours showed a statistical significant difference for the fractional synthesis rate of fibrinogen (p = 0.008) but not for albumin (p = 0.12). Repeated measurements of albumin de novo synthesis more than 48 hours apart show acceptable agreement using either one or two different isotopic labels. For fibrinogen the larger intra-individual scatter necessitates larger study groups to detect changes in longitudinal studies. Repeated measurements within 48 hours need to be validated further.

Protein Nutrition and Malnutrition in CKD and ESRD

Elevated protein catabolism and protein malnutrition are common in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). The underlying etiology includes, but is not limited to, metabolic acidosis intestinal dysbiosis; systemic inflammation with activation of complements, endothelin-1 and renin-angiotensin-aldosterone (RAAS) axis; anabolic hormone resistance; energy expenditure elevation; and uremic toxin accumulation. All of these derangements can further worsen kidney function, leading to poor patient outcomes. Many of these CKD-related derangements can be prevented and substantially reversed, representing an area of great potential to improve CKD and ESRD care. This review integrates known information and recent advances in the area of protein nutrition and malnutrition in CKD and ESRD. Management recommendations are summarized. Thorough understanding the pathogenesis and etiology of protein malnutrition in CKD and ESRD patients will undoubtedly facilitate the design and development of more effective strategies to optimize protein nutrition and improve outcomes.

Very low-protein diet plus ketoacids in chronic kidney disease and risk of death during end-stage renal disease: a historical cohort controlled study

BACKGROUND

Very low-protein intake during chronic kidney disease (CKD) improves metabolic disorders and may delay dialysis start without compromising nutritional status, but concerns have been raised on a possible negative effect on survival during dialysis. This study aimed at evaluating whether a very low-protein diet during CKD is associated with a greater risk of death while on dialysis treatment.

METHODS

This is an historical, cohort, controlled study, enrolling patients at dialysis start previously treated in a tertiary nephrology clinic with a very low-protein diet supplemented with amino acids and ketoacids (s-VLPD group, n = 184) or without s-VLPD [tertiary nephrology care (TNC) group, n = 334] and unselected patients [control (CON) group, n = 9.092]. The major outcome was survival rate during end-stage renal disease associated to s-VLPD treatment during CKD. The propensity score methods and Cox regression model were used to match groups at the start of dialysis to perform survival analysis and estimate adjusted hazard ratio (HR).

RESULTS

In s-VLPD, TNC and CON groups, average age was 67.5, 66.0 and 66.3 years, respectively (P = 0.521) and male prevalence was 55, 55 and 62%, respectively (P = 0.004). Diabetes prevalence differed in the three groups (P < 0.001), being 18, 17 and 31% in s-VLPD, CON and TNC, respectively. A different prevalence of cardiovascular (CV) disease was found (P < 0.001), being similar in TNC and CON (31 and 25%) and higher in s-VLPD (41%). Median follow-up during renal replacement therapy (RRT) was 36, 32 and 36 months in the three groups. Adjusted HR estimated on matched propensity patients was 0.59 (0.45-0.78) for s-VLPD versus CON. Subgroup analysis showed a lower mortality risk in s-VLPD versus matched-CON in younger patients (<70 years) and those without CV disease. No significant difference in HRs was found between s-VLPD and TNC.

CONCLUSION

s-VLPD during CKD does not increase mortality in the subsequent RRT period.

Effect of a low-protein diet supplemented with ketoacids on skeletal muscle atrophy and autophagy in rats with type 2 diabetic nephropathy

A low-protein diet supplemented with ketoacids maintains nutritional status in patients with diabetic nephropathy. The activation of autophagy has been shown in the skeletal muscle of diabetic and uremic rats. This study aimed to determine whether a low-protein diet supplemented with ketoacids improves muscle atrophy and decreases the increased autophagy observed in rats with type 2 diabetic nephropathy. In this study, 24-week-old Goto-Kakizaki male rats were randomly divided into groups that received either a normal protein diet (NPD group), a low-protein diet (LPD group) or a low-protein diet supplemented with ketoacids (LPD+KA group) for 24 weeks. Age- and weight-matched Wistar rats served as control animals and received a normal protein diet (control group). We found that protein restriction attenuated proteinuria and decreased blood urea nitrogen and serum creatinine levels. Compared with the NPD and LPD groups, the LPD+KA group showed a delay in body weight loss, an attenuation in soleus muscle mass loss and a decrease of the mean cross-sectional area of soleus muscle fibers. The mRNA and protein expression of autophagy-related genes, such as Beclin-1, LC3B, Bnip3, p62 and Cathepsin L, were increased in the soleus muscle of GK rats fed with NPD compared to Wistar rats. Importantly, LPD resulted in a slight reduction in the expression of autophagy-related genes; however, these differences were not statistically significant. In addition, LPD+KA abolished the upregulation of autophagy-related gene expression. Furthermore, the activation of autophagy in the NPD and LPD groups was confirmed by the appearance of autophagosomes or autolysosomes using electron microscopy, when compared with the Control and LPD+KA groups. Our results showed that LPD+KA abolished the activation of autophagy in skeletal muscle and decreased muscle loss in rats with type 2 diabetic nephropathy.

Effect of low-protein diet on kidney function in diabetic nephropathy: meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effect of low-protein diet on kidney function in patients with diabetic nephropathy.

DESIGN

A systematic review and a meta-analysis of randomised controlled trials.

DATA SOURCES

MEDLINE, EMBASE, Cochrane Library, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number (ISRCTN) Register and University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CTR) from inception to 10 December 2012. Internet searches were also carried out with general search engines (Google and Google Scholar).

STUDY SELECTION

Randomised controlled trials that compared low-protein diet versus control diet and assessed the effects on kidney function, proteinuria, glycaemic control or nutritional status.

PRIMARY AND SECONDARY OUTCOME MEASURES AND DATA SYNTHESIS

The primary outcome was a change in the glomerular filtration rate (GFR). The secondary outcomes were changes in proteinuria, post-treatment value of glycated haemoglobin A1C (HbA1c) and post-treatment value of serum albumin. The results were summarised as the mean difference for continuous outcomes and pooled by the random effects model. Subgroup analyses and sensitivity analyses were conducted regarding patient characteristics, intervention period, methodological quality and assessment of diet compliance. The assessment of diet compliance was performed based on the actual protein intake ratio (APIR) of the low-protein diet group to the control group.

RESULTS

We identified 13 randomised controlled trials enrolling 779 patients. A low-protein diet was associated with a significant improvement in GFR (5.82 ml/min/1.73 m(2), 95% CI 2.30 to 9.33, I(2)=92%; n=624). This effect was consistent across the subgroups of type of diabetes, stages of nephropathy and intervention period. However, GFR was improved only when diet compliance was fair (8.92, 95% CI 2.75 to 15.09, I(2)=92% for APIR <0.9 and 0.03, 95% CI -1.49 to 1.56, I(2)=90% for APIR ≥0.9). Proteinuria and serum albumin were not differed between the groups. HbA1c was slightly but significantly decreased in the low-protein diet group (-0.26%, 95% CI -0.35 to -0.18, I(2)=0%; n=536).

CONCLUSIONS

Low-protein diet was significantly associated with improvement of diabetic nephropathy. The adverse effects of low-protein diet were not apparent such as worsening of glycaemic control and malnutrition.

Light and shadows of dietary protein restriction in elderly with chronic kidney disease

Approximately 45% of the elderly population suffers from chronic kidney disease (CKD). The onset and the course of CKD can be ameliorated to a significant degree by several interventions, such as lowering blood pressure and serum lipid levels and achieving optimal glucose control in diabetes. In elderly patients with more advanced CKD, additional treatment may be needed. In these patients, a low-protein diet (LPD) regimen may delay the need for dialysis therapy. However, in the elderly, feasibility and compliance to LPD could be difficult and its effects are uncertain. In this contribution, we discuss the usefulness and the barriers of LPD regimen in the elderly.

Dietary treatment options for depression among diabetic patient, focusing on macronutrients

There is a bidirectional adverse association between diabetes and depression. The odds for experiencing depressive symptoms in diabetic patients are two times more than nondiabetic persons, and depression is an independent predictor for the onset of diabetes. However, depression has been approximately unrecognized and untreated in two-thirds of diabetic patients, which may lead to worsened diabetes complications. A cornerstone strategy for managing depression among diabetic patients is the use of diet to improve both health problems. Because of similar pathophysiology for chronic diseases and depression, it seems that similar dietary recommendations could be useful. However, few studies have been conducted among diabetic patients. Regarding the complications of diabetes such as renal diseases and coronary heart diseases, the proper range of various macronutrients should be clarified in depressed diabetic patients as well as the proper type of each macronutrient. In this paper, we reviewed the available data on the treatment of depression in diabetic patients.

Reduced pain and inflammation in juvenile and adult rats fed a ketogenic diet

The ketogenic diet is a high-fat, low-carbohydrate regimen that forces ketone-based rather than glucose-based cellular metabolism. Clinically, maintenance on a ketogenic diet has been proven effective in treating pediatric epilepsy and type II diabetes, and recent basic research provides evidence that ketogenic strategies offer promise in reducing brain injury. Cellular mechanisms hypothesized to be mobilized by ketone metabolism and underlying the success of ketogenic diet therapy, such as reduced reactive oxygen species and increased central adenosine, suggest that the ketolytic metabolism induced by the diet could reduce pain and inflammation. To test the effects of a ketone-based metabolism on pain and inflammation directly, we fed juvenile and adult rats a control diet (standard rodent chow) or ketogenic diet (79% fat) ad libitum for 3-4 weeks. We then quantified hindpaw thermal nociception as a pain measure and complete Freund's adjuvant-induced local hindpaw swelling and plasma extravasation (fluid movement from the vasculature) as inflammation measures. Independent of age, maintenance on a ketogenic diet reduced the peripheral inflammatory response significantly as measured by paw swelling and plasma extravasation. The ketogenic diet also induced significant thermal hypoalgesia independent of age, shown by increased hindpaw withdrawal latency in the hotplate nociception test. Anti-inflammatory and hypoalgesic diet effects were generally more robust in juveniles. The ketogenic diet elevated plasma ketones similarly in both age groups, but caused slowed body growth only in juveniles. These data suggest that applying a ketogenic diet or exploiting cellular mechanisms associated with ketone-based metabolism offers new therapeutic opportunities for controlling pain and peripheral inflammation, and that such a metabolic strategy may offer significant benefits for children and adults.