The potential role of dietary advanced glycation endproducts in the development of chronic non-infectious diseases: a narrative review.

Increasing clinical and experimental evidence accumulated during the past few decades supports an important role for dietary advanced glycation endproducts (AGE) in the pathogenesis of many chronic non-infectious diseases, such as type 2 diabetes, CVD and others, that are reaching epidemic proportions in the Western world. Although AGE are compounds widely recognised as generated in excess in the body in diabetic patients, the potential importance of exogenous AGE, mostly of dietary origin, has been largely ignored in the general nutrition audience. In the present review we aim to describe dietary AGE, their mechanisms of formation and absorption into the body as well as their main mechanisms of action. We will present in detail current evidence of their potential role in the development of several chronic non-infectious clinical conditions, some general suggestions on how to restrict them in the diet and evidence regarding the potential benefits of lowering their consumption.

Premature loss of muscle mass and function in type 2 diabetes.

INTRODUCTION: Muscle mass and function are among the most relevant factors that contribute to an optimal quality of life, and are strong predictors of mortality in the elderly. Loss of lean tissues and deterioration of muscle function have been described as one of the many complications of type 2 diabetes mellitus (DM2), but most studies do not isolate age as an intervening factor. AIM: To study whether adult DM2 patients up to 60years of age have decreased muscle mass and function compared with healthy non-diabetic (ND) subjects of similar age. METHODOLOGY: Appendicular fat-free mass (ApFFM) by dual X-ray absorptiometry (DEXA), handgrip strength (HS), quadriceps strength (QS), 12 min walking capacity (12MW) and the Timed Up and Go test (TUG) were measured in 100 DM2 patients and 39 ND controls. Muscle quality, or the ratio between lean mass and muscle strength of upper and lower limbs, and the functional limitations associated with pain and stiffness assessed according to the Western Ontario and McMaster Universities Arthrosis Index (WOMAC) were also recorded. Specific tests were performed to rule out microvascular diabetic complications (retinal and peripheral nerves), metabolic control, kidney function and vitamin D status and examine their association with ApFFM and function. RESULTS: ApFFM was significantly higher among DM2 female patients and lower among diabetic men. However opposite results were obtained when individual values were corrected for body mass index (BMI), specifically among women, who were more likely to be obese. As for muscle strength and global functionality tests, significantly better performances in TUG, 12MW, QS and HS were observed among ND subjects of both sexes. These differences prevailed even after excluding diabetic patients with microvascular complications as well as those with more than 10years of diabetes. Muscle quality was also significantly better among ND women. Higher scores of pain and stiffness in the WOMAC scale correlated with 12MW and TUG in both groups but did not correlate with ApFFM. CONCLUSIONS: We found a clear deterioration of lean mass and muscle functions among adult DM2 patients of up to 60years old, independent of length of disease, metabolic control, vitamin D status and presence of microvascular complications and pain.

Skeletal muscle ceramide species in men with abdominal obesity.

BACKGROUND: Obesity is a risk factor for diabetes and its consequences, including accelerated ageing and mortality. The underlying factor could be accumulation of certain lipid moieties, such as ceramides (CER) and diacylgycerol (DAG) within muscle tissue, which are known to promote insulin resistance (IR), induce inflammation and oxidative injury, ultimately altering muscle function. AIM: First, to study the relationship between body composition and age (independent variables) with skeletal muscle accumulation of lipid species, oxidative injury and strength. Second, to analyze the relationship between muscle tissue metabolites and insulin resistance, inflammation and lymphocyte telomere length, the latter as an indicator of ageing. METHODOLOGY: The sample included 56 healthy sedentary males, scheduled for inguinal hernia surgery, aged 27 to 80 y. Each individual was subject to anthropometric measurements, body composition assessment through radiologic densitometry (DEXA), measurement of handgrip and quadriceps strength, serum biochemical parameters (lipoproteins, creatinine, high sensitivity C reactive protein [hsCRP], fasting and post glucose insulin and glucose concentrations for calculation of IR through the Matsuda and HOMA-IR indexes), and extraction of peripheral leukocytes for measurement of telomere length. During the surgical procedure, a sample of muscle tissue was obtained (anterior abdominal oblique) in order to measure CER and DAG (and sub species according to chain length and saturation) by mass spectrometry, 4 hydroxy-2-nonenal adducts (4-HNE) using electron microscopy immunohistochemistry, and carboxymethyl-lisine (CML) by immunohistochemistry, the latter as indicators of oxidative stress (OS). RESULTS: Body mass index (BMI) of twenty six individuals was > 25 k/m2, while BMI of 7 was > 30 k/m2. Overweight/obese individuals, did not exhibit differences in skeletal muscle lipid metabolites, however total CER and specific long chain CER sub-species (20 and 22 carbon) increased significantly among individuals with a central fat distribution (n = 14) as well as in glucose intolerant subjects (n =23). A negative association was found between mononuclear leukocyte telomere length and 20 and 22 carbon CER (rho = - 0.4 and -0.5 0 p < 0.05). Muscle strength was not associated with any of the measured muscle metabolites or markers of OS. A multiple regression analysis accepted central abdominal fat and telomere length as significant predictors of CER (R2 = 0.28). CONCLUSIONS: An association was found between accumulation of specific ceramide species in muscle tissue and abdominal obesity, glucose intolerance and shortening of leukocyte telomeres, although not with muscle oxidative injury or dysfunction.

Effect of weight maintenance or gain in a 10 years period over telomere length, sirtuin 1 and 6 expression and carotid intima media thickness.

BACKGROUND: Lack of weight gain throughout adult life could mimic the beneficial effects of energy restriction in humans. The present study aimed to assess the effects of weight stability or gain, over a period of 10 years, on telomere length, sirtuin 1 and 6 expression, and carotid intima media thickness. METHODS: We studied 148 healthy adults (age range 20-59 years; 101 females) who had an objective record of their weight 10 years before. They were classified as weight losers, weight maintainers, weight gainers and extreme weight gainers. A fasting blood sample was obtained for routine laboratory and isolation of peripheral blood mononuclear cells, to extract DNA and RNA, and to measure telomere length and sirtuin 1 and 6 expression, respectively. Carotid intima media thickness was measured by ultrasound. Body composition was measured by Dual-energy X-ray absorptiometry. RESULTS: In the 10-year period, 24 participants lost weight (17 females), 65 maintained weight (41 females), 25 gained weight (15 females) and 34 were extreme weight gainers (28 females). Female weight gainers had a higher body mass index, waist circumference, total body fat and homeostatic model assessment insulin resistance. Male weight gainers had a higher hip circumference and total body fat. No differences in telomere length, sirtuin 1 expression and carotid intima media thickness were observed between weight gainers and maintainers. CONCLUSIONS: No effect of weight maintenance or gain was observed on metabolic and vascular markers of ageing.

Dietary intake increases serum levels of carboxymethil-lysine (CML) in diabetic patients.

INTRODUCTION: Advanced glycation end products are produced endogenously, in association with hyperglycemia and oxidative stress. They can also be generated during cooking or food processing and, once absorbed, alter protein function and promote inflammation. METHODS: We selected 40 healthy male subjects, 17 patients with type 2 diabetes of both sexes and 15 patients with type 1 diabetes of both sexes. Each participant underwent both a food frequency questionnaire (FFQ) and 24-hour dietary recall specially adapted for measuring CML intake, anthropometry, measurement of blood pressure and biochemical parameters in blood and urine. RESULTS: Serum CML levels were significantly higher in patients with diabetes compared to healthy subjects (p 0.04), showing a direct relationship between dietary intake and serum levels of CML in T2D patients (r 0.53 p 0.03). sCML levels correlated positively with length of diabetes mellitus, and inversely with body mass index (BMI). The most important dietary factor contributing to raise CML levels in these patients with diabetes was the consumption of milk powder. CONCLUSION: Serum levels of CML were found to be higher among diabetic subjects, associated to length of diabetes as expected, but also with the ingestion of foods containing higher amounts of ML. The consumption of milk powder in this group is a major determinant of increased serum levels.

Proliferation and differentiation of human adipocyte precursor cells: differences between the preperitoneal and subcutaneous compartments.

Human adipocyte precursor cells (APC) have been characterized in their proliferation and differentiation potential from subcutaneous, omental, and mesenteric depots, mostly from morbidly obese patients. Cells from the preperitoneal adipose compartment have not been characterized yet, least of all when obtained from normal weight subjects. The aim was to compare proliferation and differentiation of subcutaneous (SC) and preperitoneal (PP) APC derived from adipose tissue in healthy subjects with different body mass. SC and PP adipose tissue was obtained during surgery of inguinal hernias in five healthy non-obese subjects and three obese otherwise healthy men. APC, obtained by collagenase digestion, were cultured. Proliferation was assayed by cell counting and differentiation by oil red O staining and flow cytometry using Nile Red staining. Proliferation of SC was higher than PP APC. Such differences between both compartments were even higher in APC obtained from obese patients. Conversely PP APC differentiated earlier in vitro compared with SC cells. These results agree with published data on fat cell proliferation. However regarding differentiation, our data show that APC from deeper depots (in this case PP) differentiate earlier than subcutaneous APC. This is different to previous studies performed in mesenteric or omental adipose tissue.

Fluorescent serum and urinary advanced glycoxidation end-products in non- diabetic subjects

Introduction: Advanced glycoxidation end-products (AGEs) are involved in age-related conditions and diabetic complications. Diet intake contributes to their circulating concentrations. Aim: To measure serum and urinary AGEs in non-diabetic volunteers and relate their concentration to body composition, blood chemistry and dietary ingesti¢n. Methods: We studied 41 adult men (31 middle-aged adults and 10 elderly). A nutritional assessment including a dietary recall designed for detection of AGE ingesti¢n (specifically carboxymethyl-lysine(CML)), and anthropometric measurements were performed. Also serum lipoproteins, insulin, glucose, leptin and C reactive protein (CRP). AGEs were measured in serum and urine samples using size exclusion chromatography and flow injection assay (FIA); the technical procedures were first employed in 11 heterogeneous diabetics, as positive controls for this methodology. Results: Serum and urinary chromatograms indicated that areas under the curve were not different in younger compared with elderly adults. AGEs did not correlate with dietary intake, body composition, nor metabolic parameters, however they correlated significantly with renal function and CRP concentration. Discussion: In these non-diabetic volunteers, with low CML intake, serum and urinary concentration of AGEs were not related to dietary intake. AGEs were related to renal function and CRP, but not to body composition, lipoproteins, insulin and glucose.

[The importance of folic acid in current medicine]. / Importancia del ácido fólico en la medicina actual.

Lately, folic acid deficiency is gaining a predominant role in the pathogenesis of congenital malformations and cardiovascular diseases in adults. The planning of individual and population preventive strategies for these diseases must consider this deficiency. This paper reviews the anatomical, biochemical and molecular bases of neural tube defects and cardiovascular diseases in adults. In these two frequent diseases, folic acid supplementation has shown a clear cut protective effect.

Changes in microsomal activity in alcoholism and obesity.

BACKGROUND: Liver damage is more prevalent among obese alcoholics, and cytochrome P-4502E1(CYP2E1) induction is involved in its pathogenesis. OBJECTIVES: The study was undertaken to assess microsomal function, in alcoholic and nonalcoholic male subjects with different body compositions, through pharmacokinetics of chlorzoxazone (CLZ). We also intended to study the relationship between CLZ hydroxylation and urinary levels of 8-hydroxydiguanosine, and between CLZ levels and liver histology. METHODS: Serial measurements of CLZ serum concentration, after a 750 mg dose, were performed in 17 alcoholics (9 normal weight and 8 obese) and 21 nonalcoholic subjects (10 normal weight and 11 obese). Concentration of 6-hydroxy-chlorzoxazone (6-OH-CLZ) was determined at the second hour. Anthropometry, clinical laboratory tests, and urinary 8-hydroxydiguanosine concentrations were measured. Liver biopsies were performed in alcoholics. RESULTS: Five biopsies revealed severe lesions, one in normal-weight and four in obese patients (p = NS). Area under the curve (AUC) of CLZ was higher in normal-weight controls compared with the rest of the groups (ANOVA p = 0.001). This parameter correlated negatively with adiposity in nonalcoholic subjects and did not correlate with liver histology. 6-OH-CLZ/CLZ ratio was lower in normal-weight controls, compared with obese subjects and normal-weight alcoholics (p = 0.02). Both alcoholism and obesity were included as predictors of CLZ AUC in a multiple regression analysis. The two-factor ANOVA showed an additive effect of centripetal body fat distribution and alcoholism. Urinary 8-hydroxydiguanosine levels were extremely variable. CONCLUSIONS: Centripetal adiposity and alcoholism are associated with induction of CYP2E1. This may explain the higher prevalence of liver damage among obese alcoholics and also nonalcoholic steatohepatitis.

Nutritional support in alcoholic cirrhotic patients improves host defenses.

BACKGROUND: Malnutrition is usual in patients with alcoholic liver disease and is associated with a poor outcome. Nutritional support decreases nutrition-associated complications. AIM: To demonstrate that nutritional support in ambulatory alcoholic cirrhotic patients improves host defenses. METHODS: Thirty-one male outpatients with alcoholic cirrhosis CHILD-PUGH B or C were included. Twenty-five subjects completed six months consuming daily a nutritional supplement (Ensure, 1000 Kcal and 35 g protein), in addition to their regular diet. At entrance and every three months, a clinical assessment, nutritional evaluation and indirect calorimetry were performed. Liver function tests and LPS-induced monocyte production of cytokines, salivary secretory IgA, lactulose/mannitol ratio and breath hydrogen tests were also measured in these intervals. Delayed cutaneous hypersensitivity and IgG and IgM antibody response to endotoxin were assessed at entrance and at the end of the study. RESULTS: Patients drank 85% of the provided supplement as an average. REE, total body fat and serum albumin increased, basal breath hydrogen decreased and cellular immunity improved significantly during the follow up period (p< or =0.03). All the other parameters remained unchanged throughout the study. Six patients (16.2%) died during the study, five due to upper gastrointestinal bleeding. CONCLUSION: Nutritional support in alcoholic cirrhotic patients improves nutritional status and cell mediated immunity.

[New pieces in the puzzle of atherogenesis]. / Nuevas piezas en el puzzle de la aterogénesis.

The contribution of high serum levels of cholesterol to atherogenesis has been widely recognized, but the mechanisms are not completely clear. Numerous publications have emphasized that oxidized, but not native low-density lipoproteins, are the particles incorporated into the arterial wall. A group of receptors generically called "scavenger" (SR), actively bind these modified lipoproteins and incorporate them into monocytes-macrophages, in the arterial intima. SR are not down regulated by intracellular concentrations of cholesterol, thus accumulating huge amounts of lipids, transforming monocyte-macrophages into foam cells, predominant cell type of the fatty streak. The simultaneous cytokine production and migration of other cellular types progressively transform this initial lesion into the organized atherosclerotic plaque. In this setting SR, which are up-regulated by oxidized LDL, play a central promoting role. Its presence has been demonstrated in arterial plaques both in human and animal models, and its blockade protects animals from development or progression of atherosclerosis. In humans, elevated antibody titers to oxidized LDL in patients with coronary stenosis, and increased SR activity, in pro-atherogenic conditions such as haemodialysis, indicate that this model may operate as well, but the evidences are still not solid enough to definitively conclude that the oxidized-LDL-SR hypothesis is a finished puzzle.

Lipid turnover in alcoholics before and after an ethanol load.

Alcohol ingestion decreases plasma free fatty acids (FFAs) and lipid oxidation. This study was conducted to determine palmitate turnover in alcoholics during a short abstinence period and after an ethanol load and in a group of nonalcoholic control subjects, looking for correlations between palmitate turnover, FFA, acetate, and acetoacetate/beta hydroxybutyrate ratio (AKBR). Palmitate C14 turnover was studied in five alcoholics during early abstinence and after a 0.8 g/kg ethanol load, and in five nonalcoholic normal controls. Plasma levels of FFA, acetate, acetoacetate, and beta hydroxybutyrate were measured before and during the ethanol load. A needle hepatic biopsy was performed in alcoholics. FFA levels, palmitate flux, oxidation, and nonoxidative disposal were similar in alcoholics compared with control subjects, decreasing significantly after the ethanol load in both groups. AKBR and ketone bodies were similar in both groups in the basal period. After the alcohol infusion, AKBR decreased significantly. Acetoacetate levels did not change, and beta hydroxybutyrate and total ketone bodies increased significantly in alcoholics and control subjects. A positive correlation was found between FFA levels and palmitate flux. Liver biopsies showed mild changes in the patients studied. The similar inhibition of lipid turnover, FFA release, and the drop in AKBR observed after an alcohol load in alcoholics and control subjects suggest that this effect is mediated by alcohol metabolism and not by metabolic alterations present in alcoholics.

[Markers of hepatic fibrogenesis in alcoholic patients]. / Marcadores de fibrogénesis hepática en pacientes alcohólicos.

BACKGROUND: An elevation of serologic markers of hepatic fibrogenesis has been reported in liver diseases of different etiologies. Among these, the N-terminal type III procollagen (P-III-P) and the P1 proteolytic fragment of laminin (P1 laminin) increase in alcoholic liver damage, in proportion to the progression of this condition. AIM: To study serum levels of P-III-P and P1 laminin in asymptomatic alcoholics with and without liver damage and decompensated alcoholic cirrhotics, compared to normal controls. METHODS: Serum P-III-P and laminin levels were measured in asymptomatic alcoholics during detoxification treatment. Liver biopsies were obtained, in order to detect liver damage, which was graded with a numeric score, considering values over 6 as severe damage. Serum fibrogenesis markers were also measured in a group of decompensated alcoholic cirrhotics. RESULTS: P-III-P levels were significantly higher in cirrhotic patients compared to alcoholics with or without liver damage and to normal controls. Laminin was not different between groups. P-III-P did not correlate with histologic score in asymptomatic patients. CONCLUSIONS: In this study P-III-P and P1 laminin were not usefull discriminators of severe liver damage among asymptomatic alcoholics; their levels were found to rise significantly only when liver disease has become clinically evident.

Fatty acid composition of liver total lipids in alcoholic patients with and without liver damage.

Alcohol ingestion may promote lipid peroxidation, and the presence of polyunsaturated fatty acids in liver lipids may be essential for the generation of liver damage through this mechanism. The aim of this study is to examine fatty acid composition of liver lipids in chronic alcoholics with and without histological liver damage. A percutaneous liver biopsy was performed to 28 patients hospitalized for treatment of their alcoholism. Liver total lipids were extracted from a portion of the tissue sample and fatty acid composition was measured by gas chromatography. Another piece of the sample was sent for histological study. Six patients had histological cirrhosis or alcoholic hepatitis in their biopsies, the rest of the patients had minimal changes. Patients with liver damage had higher levels of oleic acid and total monoenoic fatty acids, a higher 18:1/18:0 ratio, lower levels of polyunsaturated fatty acids, a lower 20:4/18:2 ratio, and a lower peroxidability index in liver total lipids, than patients without liver damage. Alcoholic patients with asymptomatic liver damage have less unsaturated fatty acids in liver total lipids than their counterparts with normal livers.

Interleukin 1 and tumor necrosis factor in obese alcoholics compared with normal-weight patients.

We performed a liver biopsy and measured plasma concentrations of interleukin 1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha), and spontaneous and lipopolysaccharide-stimulated in vitro monocyte production of IL-1 beta and TNF-alpha in 19 obese and 17 age-matched, normal-weight alcoholics admitted for treatment of their alcoholism. Nine healthy normal-weight alcoholics had cirrhosis in their liver biopsy (Fisher's exact test: P=0.031). A histologic score (derived from the sum of fat, necrosis, fibrosis, and inflammation in the biopsy) correlated with body mass index and the percentage body fat, calculated by using the sum of four skinfold-thickness measures. Plasma concentrations and spontaneous in vitro monocyte production of IL-1 beta and TNF-alpha were below detection limits. No significant differences were observed between normal-weight and obese alcoholics with or without cirrhosis and normal control subjects in lipopolysaccharide-stimulated monocyte production of IL-1 beta (6.5 +/- 0.8, 10.1 +/- 2.7, 7.9 +/- 1.6, and 5.28 +/- 4.24 micrograms/L, respectively) or TNF-alpha (2.8 +/- 0.4, 3.7 +/- 1.0, 3.0 +/- 0.44, and 1.97 +/- 1.01 micrograms/L, respectively). However, a positive correlation was found between IL-1 beta production and body mass index (r=0.333, P=0.047), percentage body fat (r=0.412, p=0.013), abdominal circumference (r=0.416, P=0.012), and total histologic score (r=0.331, P=0.049). A multiple-regression model accepted abdominal circumference as the only independent predictor of IL-1 beta production. TNF-alpha did not correlate with any of the above-mentioned indexes. We conclude that obese alcoholics have a higher frequency of histologic liver damage and that IL- 1 beta production by stimulated monocytes is related to abdominal fat accumulation.

[Major histocompatibility system as a risk factor for alcoholic liver disease]. / El sistema mayor de histocompatibilidad como factor de riesgo de la enfermedad hepática alcohólica.

Several associations between alleles of the major histocompatibility system and alcoholic liver disease have been described. However, these are weak and change from one population to another. The aim of this work was to search for a possible genetic risk factor for alcoholic liver disease among Chilean alcoholics. We studied blood groups, serum proteins and HLA antigens in 39 alcoholic cirrhotics, 104 asymptomatic alcoholics and 44 non alcoholic controls. Asymptomatic alcoholics were also subjected to a percutaneous liver biopsy that showed moderate to severe histological liver damage in 46 subjects (44%). No differences in the studied genetic markers, were found among the four groups. It is concluded that this study does not confirm previously reported associations between genetic markers and alcoholic liver disease.

Suprahepatic vein oxygen tension in alcoholics with severe and mild liver damage.

We measured suprahepatic vein and arterial partial oxygen pressure in 35 alcoholics with severe (N = 7) or mild (N = 28) histological liver damage and without evidence of clinical liver failure. The suprahepatic vein was punctured with a fine needle, using a percutaneous approach. Suprahepatic vein partial oxygen pressure was lower and arterial-suprahepatic gradient higher in alcoholics with severe liver damage compared to those with mild damage (35.1 +/- 1.7 vs 44.1 +/- 2.1 and 58.9 +/- 3.7 vs 45.9 +/- 2.4 mm Hg, respectively; P < 0.001). Suprahepatic puncture was well tolerated and devoid of complications. It is concluded that alcoholics with severe liver damage have lower oxygen tensions in the suprahepatic vein, a phenomenon that supports the hypoxic theory of alcoholic liver disease.

Effects of long-term vitamin E supplementation in alcoholic cirrhotics.

OBJECTIVE: Alcohol ingestion promotes lipoperoxidation and alters cellular antioxidant mechanisms. Alpha-tocopherol levels decrease in alcoholics as severity of liver damage increases. The aim of this protocol was to study the effects of a long-term oral 500 mg vitamin E daily supplementation in decompensated ambulatory alcoholic cirrhotics. PATIENTS AND METHODS: 67 subjects were included in this double blind trial; 33 patients received vitamin E and 34 patients received placebo tablets of identical appearance during 1 year. Each month, the patients were seen by a nurse practitioner who was in charge of detecting alcohol ingestion and checking adherence to treatment. Every 3 months, the patients underwent a medical examination, and blood samples were taken for clinical laboratory analysis and serum vitamin E measurement. RESULTS: Alpha-tocopherol levels were significantly lower in patients with more severe liver disease. This difference was not significant when vitamin E levels were corrected by cholesterol. Oral supplementation significantly increased serum vitamin E levels in the experimental group. Alcohol ingestion and hospitalization rates were similar in both groups. Life table analysis did not show significant differences in mortality between the two groups. DISCUSSION: Vitamin E supplementation with adequate doses of an alpha-tocopheryl acetate formulation during 1 year did not influence hepatic laboratory parameters, mortality or hospitalization rates of decompensated alcoholic cirrhotics, although serum levels of the vitamin significantly increased.