Fructose-Rich Diet Is a Risk Factor for Metabolic Syndrome, Proximal Tubule Injury and Urolithiasis in Rats.

Excessive consumption of fructose (FR) leads to obesity, metabolic syndrome (MS) and insulin resistance, which are known risk factors for kidney stones. The epidemiological study has suggested the association between fructose consumption and urolithiasis, but the precise mechanism is still not well understood. Male Wistar rats were assigned for 8 weeks to three groups with different FR content in diet: RD (n = 5)-regular diet with a FR < 3%; F10 (n = 6)-regular diet with an addition of 10% Fr in drinking water; F60 (n = 5)-60% FR as a solid food. Serum concentration of FR, creatinine (Cr), insulin (Ins), triglycerides (Tg), homocysteine (HCS), uric acid (UA), calcium (Ca), phosphate (Pi), magnesium (Mg) and sodium (Na) were measured. Based on 24 h urine collection the following tests were performed: urine pH, proteinuria (PCR), excretion of N-Acetyl-(D)-Glucosaminidase (NAG), monocyte chemoattractant protein (MCP-1), uric acid (uUAEx), phosphate (uPiEx), calcium (uCaEx), magnesium (uMgEx) and sodium (uNaEx). The creatinine clearance (CrCl) was calculated. Calcium deposits in kidney sections were examined using hematoxylin and eosin (HE) and von Kossa stains. The rats on F10 and F60, as compared to the RD diet, showed a tendency for lower CrCl, higher HCS level and some features of MS as higher Ins and TG levels. Interestingly, F10 (fluid) versus F60 (solid) diet led to higher serum Ins levels. F10 and F60 versus RD demonstrated higher urinary excretion of MCP-1 and NAG which were suggestive for inflammatory injury of the proximal tubule. F10 and F60 as compared to RD showed significantly lower uUAEx, although there were no differences in clearance and fractional excretion of UA. F60 versus RD induced severe phosphaturia (>30×) and natriuria (4×) and mild calciuria. F10 versus RD induced calciuria (3×), phosphaturia (2×) and mild natriuria. Calcium phosphate stones within the tubules and interstitium were found only in rats on FR diet, respectively, in two rats from the F10 group and another two in the F60 group. The rats which developed stones were characterized by significantly higher serum insulin concentration and urinary excretion of calcium and magnesium. A fructose-rich diet may promote development of calcium stones due to proximal tubule injury and metabolic syndrome.

Impact of fructose diet and renal failure on the function of pancreatic islets.

OBJECTIVES: This study was designed to evaluate the impact of fructose-rich diet and chronic kidney disease (CKD) on the in vitro function of pancreatic islets. METHODS: Fifty-four rats were divided into 3 equal groups as follows: control, rats with CKD 1/2 that underwent surgical uninephrectomy, and rats with CKD 5/6 that underwent uninephrectomy and kidney cortex mass resection. Each group was further assigned to 3 diet protocols--regular diet, regular diet with 10% fructose (F10), and 60% fructose-rich diet (F60). After 8 weeks of insulin administration, C-peptide, glycated hemoglobin level, serum urea nitrogen, creatinine clearance, and homeostasis model assessment of insulin resistance were evaluated. Static glucose insulin stimulation test of isolated pancreatic islets and histologic analysis of pancreatic tissue were performed. RESULTS: The F10 diet increased the levels of insulin and C-peptide in all groups. Homeostasis model assessment of insulin resistance was increased in all animals fed with fructose. The elevated levels of creatinine and diminished creatinine clearance were detected in CKD 5/6 rats fed with 60% fructose-rich diet. The F10 diet resulted in high levels of serum insulin and C-peptide and glucose-stimulated insulin secretion. Fructose-rich diet increased the islet size and number, with irregular morphology and exocrine tissue fibrosis. CONCLUSIONS: The fructose-rich diet accelerates the progression of CKD and affects the pancreatic islet function.

Decreased hypoxia-inducible factor-1α in gastrocnemius muscle in rats with chronic kidney disease.

BACKGROUND/AIMS: Hypoxia-inducible factor (HIF)-1α is responsible for increased expression of genes engaged in angiogenesis. Our previous study indicated capillary rarefaction and atrophy of glycolytic fibers, mainly in locomotor muscles of uremic animals. Perhaps these changes are secondary to disturbances of HIF-1α in skeletal muscles. METHODS: Expression of HIF-1α at mRNA and protein levels, as well as mRNA of vascular endothelial growth factor A (VEGF-A), vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS), in gastrocnemius muscle (MG) and longissimus thoracic muscle (ML) were measured by RT-PCR and Western blot. Rats were randomized to subtotal nephrectomy (CKD5/6), uninephrectomy (CKD1/2) or sham operation (controls). RESULTS: For CKD5/6 versus controls, mRNA levels for HIF-1α, VEGF-A, VEGFR-1 and VEGFR-2 were significantly reduced only in MG, while eNOS was significantly decreased and iNOS was significantly increased only in ML. Western blot analysis indicated significantly increased HIF-1α protein levels in MG and ML from CKD1/2 animals versus controls, whereas in the CKD5/6 group, the level of HIF-1α protein decreased significantly in MG and increased significantly in ML versus controls and CKD1/2. CONCLUSION: The reduced expression of HIF-1α mRNA and protein in locomotor muscle from CKD5/6 animals may be involved in the pathogenesis of uremic myopathy. Increased expression of iNOS in the postural muscles may act as a protective factor through HIF-1α stabilization.

Low-fructose diet lowers blood pressure and inflammation in patients with chronic kidney disease.

BACKGROUND: Fructose has been strongly linked with hypertension, hyperuricemia and inflammation in experimental models and humans. However, the effect of low-fructose diet on inflammation, hyperuricemia and the progression of renal disease has not yet been evaluated in patients with chronic kidney disease (CKD). METHODS: Twenty-eight patients (age 59 ± 15 years, 17 males/11 females) with Stages 2 and 3 CKD were switched from a regular (basal) (60.0 g/24 h) to a low (12.0 g/24 h) fructose diet for 6 weeks, followed by a resumption of their regular diet for another 6 weeks. Diet was monitored by a dietician. At the baseline, low- and regular-fructose diet ambulatory blood pressure (BP) was measured and blood sampled for renal function (creatinine), inflammatory markers, fasting glucose and insulin and serum uric acid. Twenty-four-hour urine collections were also obtained for creatinine, uric acid, monocyte chemotatic protein-1, transforming growth factor-beta and N-acetyl-beta-D-glucosaminidase. RESULTS: The low-fructose diet tended to improve BP for the whole group (n = 28), while significant reduction of BP was only seen in dippers (n = 20) but not in non-dippers (n = 8). No effects on estimated glomerular filtration rate (eGFR) or proteinuria were observed. Serum uric acid was lowered non-significantly with low-fructose diet (7.1 ± 1.3 versus 6.6 ± 1.0 mg/dL, P < 0.1), whereas a significant decrease in fasting serum insulin was observed (11.2 ± 6.1 versus 8.2 ± 2.9 mIU/mL, P < 0.05) and the reduction persisted after return to the regular diet. A slight but not significant reduction in urinary uric acid and fractional uric acid excretion was observed while the patients were on the low fructose diet. The low-fructose diet also decreased high sensitivity C-reactive protein (hsCRP) (4.3 ± 4.9 versus 3.3 ± 4.5 mg/L; P < 0.01) and soluble intercellular adhesion molecule (sICAM) (250.9 ± 59.4 versus 227 ± 50.5 ng/mL; P < 0.05). The hsCRP returned to baseline with resumption of the regular diet, whereas the reduction in sICAM persisted. CONCLUSION: Low-fructose diet in subjects with CKD can reduce inflammation with some potential benefits on BP. This pilot study needs to be confirmed by a larger clinical trial to determine the long-term benefit of a low-fructose diet compared to other diets in subjects with CKD.

Influence of different stages of experimental chronic kidney disease on rats locomotor and postural skeletal muscles microcirculation.

BACKGROUND: Chronic kidney disease (CKD) is associated with muscle excess fatigue and diminished maximal whole body oxygen consumption, which in part could be depended on poor muscle microcirculatory network. The aim of this study was to assume the influence of different stages of CKD on microcirculation vessels in functionally different skeletal muscles--locomotor, the gastrocnemius muscle, and postural, the longissimus thoracis muscle. METHODS: Male Wistar rats underwent sham operation (CON), uninephrectomy (CKD 1/2) and subtotal nephrectomy (CKD 5/6). Muscle samples were stained for an alkaline phosphatase to differentiate capillaries. The number of capillaries was estimated by a single observer in 10 microm transverse sections by point counting at a magnification of x 125 using an Image Analysis System Q 500 MC of Leica. Blood pressure and serum creatinine, haptoglobin, MCP-1, VEGF, and PDGF were measured. RESULTS: There were significant differences (p < 0.05) in CD (number of capillaries per 1 mm(2) of muscle tissue), C:F (capillary to fiber ratio), and CC/F (capillary contact per fiber). The CKD 1/2 group in gastrocnemius and longissimus muscle had 53% and 33% lower C:F; 56% and 33% lower CD; and 44% and 20% less CC/F than CON, respectively. The CKD 5/6 group in gastrocnemius and longissimus muscle had 46% and 20% lower C:F; 47% and 11% lower CD; and 48% and 25% less CC/F versus control, respectively. Blood pressure was higher in CKD 5/6 vs. CKD 1/2 and CON (145/95 vs. 107/87 and 119/77 mmHg, p < 0.05, respectively). CKD 5/6 had higher creatinine than CKD 1/2 and CON (1.22 vs. 0.83 and 0.74 mg/dL, p < 0.05, respectively). Haptoglobin was higher in CKD 1/2 and CKD 5/6 versus CON (1.68 and 1.63 vs. 0.70 mg/mL, p < 0.05, respectively). MCP-1 was higher in CKD 5/6 and CKD 1/2 versus CON (609 and 489 vs. 292 pg/mL, p < 0.05, respectively). There were no significant differences in serum growth factors concentration between groups. CONCLUSION: Capillary rarefaction is present in early stages of CKD. These changes are independent of blood pressure and progression of CKD. We suspected that muscle function has a big impact on microvasculature as capillaries rarefaction has been reduced more in locomotor than postural skeletal muscle.

Anderson-Fabry disease: diagnostic problems from gastrointestinal manifestations to the diagnosis of kidney disease.

We report a case of a 52-year-old male who has been diagnosed for many years because of chronic diarrhea and proteinuria with concomitant gradually progressing chronic kidney disease. Diagnostic problems associated with the initial diagnosis of amyloidosis as a primary cause of the patient's complaints have been described. Anderson-Fabry disease (AFD) was suspected following comprehensive evaluation that resulted eventually in the exclusion of amyloidosis and the echocardiographic examination showing hypertrophic cardiomyopathy in the patient with no history of hypertension and aortic valve defects. The diagnosis of AFD was confirmed by results of enzymatic tests.

Cardiac troponin I in patients with chronic kidney disease treated conservatively or undergoing long-term haemodialysis.

BACKGROUND: Cardiac troponin I (cTnI) has been shown to be a specific marker of myocardial damage in the general population. In patients suffering from chronic kidney disease (CKD) cTnI may be increased in serum without other signs of acute myocardial damage confusing the diagnosis. AIM: To compare cTnI concentration in CKD patients, treated conservatively or with haemodialysis, with healthy controls, and to evaluate the cardiovascular risk factor profile in these groups. METHODS: The study population consisted of three groups: group I (n=10, 5 women, 5 men, mean age 32+/-4 years) - healthy, young volunteers without kidney diseases with creatinine clearance (CrCl) 97.13+/-23.24 ml/min; group II (n=21, 8 women, 13 men, mean age 51+/-15 years) - patients with CKD in stages 3-5 with CrCl=34.04+/-18.34 ml/min; and group III (n=30, 14 women, 16 men, mean age 50+/-14 years) - patients on long-term haemodialysis. The cTnI level was measured using an AxSYM analyzer (Abbott). In group III blood was taken before the haemodialysis session. The high sensitivity C-reactive protein (hsCRP), haemoglobin, parathyroid hormone (PTH) and phosphorus levels were determined. Blood pressure was also recorded. Echocardiography was performed and left ventricular mass index (LVMI) was calculated on the basis of the Devereux and Reichek formula. RESULTS: Compared with controls, the cTnI values were significantly higher in patients from group III and tended to be higher in patients from group II (0.01+/-0.03 vs. 0.063+/-0.08 and 0.066+/-0.162 ng/ml, respectively, p <0.05 and NS). In 46% of haemodialysed patients cTnI concentration was above the value of the 99th percentile in the apparently, healthy population but did not exceed the acute myocardial infarction diagnostic cut-off. The high sensitivity C-reactive protein value was significantly higher in groups III and II versus controls (4.92+/-5.12 and 2.26+/-2 vs. 0.85+/-0.48 mg/dl, p <0.05 respectively). The LVMI values were significantly higher in groups III and II than in controls (159+/-46 and 113+/-35 vs. 81+/-14 g/m2, respectively). There was a significant correlation between hsCRP and LVMI in group II (r=0.49, p <0.05). Blood pressure was significantly higher in groups III and II compared to controls (129+/-25 and 137+/-19 vs. 116+/-7 mmHg, respectively). Patients from group III had significantly decreased haemoglobin value and increased PTH as well as phosphorus concentration compared to subject from group II and controls. CONCLUSION: Chronic kidney disease is associated with accumulation of cardiovascular risk factors and increased cTnI concentration.

Inflammation, malnutrition and vascular contraction in experimental chronic kidney disease.

BACKGROUND: Inflammation is a well-defined factor influencing the development of cardiovascular complications in chronic renal failure. The aim of this study was to examine systemic inflammatory state defined by the level of serum haptoglobin, local inflammation defined by monocyte chemoattractant protein-1 (MCP-1) level and arterial response to phenylephrine in different stages of renal failure. METHODS: Experiments were performed on male Wistar rats, weighing 290-380 g. The rats were divided into 4 groups: I (control) was shame-operated (n=12); II underwent 1/2 nephrectomy (n=12); III, 3/4 nephrectomy (n=8); IV 5/6 nephrectomy (n=12). After 4 weeks, blood pressure (BP) in carotid artery was measured, and blood was collected for blood urea nitrogen, creatinine, albumin, haptoglobin and MCP-1. We compared the smooth muscle contractility after stimulation of alpha1-adrenoreceptor with phenylephrine in all groups. The constriction of artery was measured as the increase in perfusion pressure at a constant flow of the perfusion fluid. Cumulative response curves (CRCs) were obtained using the van Rossum method. RESULTS: We observed a significant shift of CRCs to the left in group III (calculated half-maximal contraction [EC50] was 1.55 x 10(-7) M/L vs. 7.71 x 10(-7) M/L in control) and a nonsignificant shift of CRCs to the left in group II (3.62 x 10(-7) M/L). Unexpectedly, rat tail arteries from the rats in the 5/6 nephrectomy group were characterized by diminished contraction response to phenylephrine (EC50 9.57 x 10-7 M/L). Systemic inflammation defined by haptoglobin level occurred in the 1/2 nephrectomy group and did not increase in more advanced stages of renal disease. Local inflammation (MCP-1 level) increased together with the renal failure progression. We found a positive correlation between MCP-1 level and haptoglobin only in the 5/6 nephrectomy group (r=0.65; p<0.01). CONCLUSION: The inflammatory state which affects vascular smooth muscle cells plays a key role in determining vascular contraction and resistant artery tone.