Sarcopenic obesity in free-living older adults detected by the ESPEN-EASO consensus diagnostic algorithm: Validation in an Italian cohort and predictive value of insulin resistance and altered plasma ghrelin profile.

Aging and obesity are synergistic sarcopenia risk factors (RF). Their association in sarcopenic obesity (SO) enhances morbidity and mortality, but consensus on SO diagnostic criteria is limited. ESPEN and EASO issued a consensus algorithm for SO screening (obesity and clinical SO suspicion) and diagnosis [low muscle strength by hand-grip (HGS) and low muscle mass by BIA], and we investigated its implementation in older adults (>65-years), as well as SO-associated metabolic RF [insulin resistance (IR: HOMA) and plasma acylated (AG) and unacylated (UnAG) ghrelin, with predictive value also assessed from 5-year-prior observations]. Older adults with obesity from the Italian MoMa study on metabolic syndrome in primary care (n = 76) were studied. 7 of 61 individuals with positive screening had SO (SO+; 9 % of cohort). No individuals with negative screening had SO. SO+ had higher IR, AG and plasma AG/UnAG ratio (p < 0.05 vs negative screening and SO-), and both IR and ghrelin profile predicted 5-year SO risk independent of age, sex and BMI. The current results provide the first ESPEN-EASO algorithm-based investigation of SO in free-living older adults, with 9 % prevalence in those with obesity and 100 % algorithm sensitivity, and they support IR and plasma ghrelin profile as SO risk factors in this setting.

Central adiposity markers, plasma lipid profile and cardiometabolic risk prediction in overweight-obese individuals.

BACKGROUND: Waist circumference (WC) is the currently recommended marker of central fat for cardiometabolic risk screening. Alternative surrogate markers have been recently proposed to better reflect the metabolic impact of central fat accumulation per se, based on WC normalization by height (Weight-to-Height Ratio - WtoH; Body Roundness Index - BRI) or body mass index (BMI) without (A Body Shape Index - ABSI) or with inclusion of plasma triglyceride and HDL-cholesterol concentrations (Visceral Adiposity Index - VAI). METHODS: We investigated associations between WtoH, BRI, ABSI or VAI and insulin resistance (HOMA-index) or metabolic syndrome (MetS) in a general population cohort from the North-East Italy Mo.Ma. study (n = 1965, age = 49 ± 13 years, BMI = 26.7 ± 5.2 kg/m2). Baseline values were also evaluated as predictors of future insulin resistance and MetS in overweight-obese individuals undergoing 5-year follow-up (Ow-Ob) (n = 263; age = 54 ± 9, BMI = 30,7 ± 4,1). RESULTS: Compared to WC or BMI, basal WtoH and BRI were similarly associated with baseline HOMA and MetS prevalence after multiple adjustments (P < 0.001) and all markers similarly predicted 5-year HOMA and MetS (P < 0.001). Under basal conditions, superimposable results were observed for VAI whereas ABSI was less accurate or unable to identify baseline HOMA and MetS (p < 0.05 vs WtoH-BRI-VAI-WC-BMI). VAI had highest 5-year risk predictive value in Ow-Ob [ROC Area Under the Curve (AUC) VAI > WtoH-BRI-WC-BMI; p < 0.05] while no predictive value was in contrast observed for ABSI (ROC AUC ABSI < WtoH-BRI-WC-BMI; p < 0.05). Using alternate formulae with plasma lipid inclusion in ABSI and removal from VAI calculations completely reversed their 5-year predictive value and AUC. CONCLUSIONS: The current findings do not support replacement of WC with height-normalized anthropometric central fat surrogate markers to predict cardiometabolic risk in the general and overweight-obese population. BMI-normalization impairs risk assessment unless plasma lipid concentrations are available and included in calculations.

Unacylated Ghrelin: A Novel Regulator of Muscle Intermediate Metabolism With Potential Beneficial Effects in Chronic Kidney Disease.

In patients with chronic kidney disease (CKD), malnutrition with loss of skeletal muscle mass has a negative impact on morbidity and mortality. Emerging evidence indicates that a cluster of oxidative stress, inflammation, and insulin resistance directly contributes to skeletal muscle catabolism by favoring protein breakdown over synthesis. Ghrelin is a gastric hormone discovered and initially studied in its acylated orexigenic form. More recently, a role of unacylated ghrelin (UnAG) has been described to reduce skeletal muscle mitochondrial reactive oxygen species generation, inflammation, and insulin resistance both in experimental models and in clinical studies. UnAG administration could therefore represent a potential comprehensive therapeutic approach for CKD-related metabolic and nutritional complications. Studies of UnAG administration in experimental and clinical CKD are needed to test the hypothesis that UnAG may chronically improve nutritional status and outcome in CKD patients.

Unacylated ghrelin normalizes skeletal muscle oxidative stress and prevents muscle catabolism by enhancing tissue mitophagy in experimental chronic kidney disease.

Unacylated ghrelin (UnAG) may lower skeletal muscle oxidative stress, inflammation, and insulin resistance in lean and obese rodents. UnAG-induced autophagy activation may contribute to these effects, likely involving removal of dysfunctional mitochondria (mitophagy) and redox state maintenance. In chronic kidney disease (CKD) oxidative stress, inflammation and insulin resistance may negatively influence patient outcome by worsening nutritional state through muscle mass loss. Here we show in a 5/6 nephrectomy (Nx) CKD rat model that 4 d s.c. UnAG administration (200 µg twice a day) normalizes CKD-induced loss of gastrocnemius muscle mass and a cluster of high tissue mitochondrial reactive oxygen species generation, high proinflammatory cytokines, and low insulin signaling activation. Consistent with these results, human uremic serum enhanced mitochondrial reactive oxygen species generation and lowered insulin signaling activation in C2C12 myotubes while concomitant UnAG incubation completely prevented these effects. Importantly, UnAG enhanced muscle mitophagy in vivo and silencing RNA-mediated autophagy protein 5 silencing blocked UnAG activities in myotubes. UnAG therefore normalizes CKD-induced skeletal muscle oxidative stress, inflammation, and low insulin signaling as well as muscle loss. UnAG effects are mediated by autophagy activation at the mitochondrial level. UnAG administration and mitophagy activation are novel potential therapeutic strategies for skeletal muscle metabolic abnormalities and their negative clinical impact in CKD.-Gortan Cappellari, G., Semolic, A., Ruozi, G., Vinci, P., Guarnieri, G., Bortolotti, F., Barbetta, D., Zanetti, M., Giacca, M., Barazzoni, R. Unacylated ghrelin normalizes skeletal muscle oxidative stress and prevents muscle catabolism by enhancing tissue mitophagy in experimental chronic kidney disease.

Unacylated Ghrelin Reduces Skeletal Muscle Reactive Oxygen Species Generation and Inflammation and Prevents High-Fat Diet-Induced Hyperglycemia and Whole-Body Insulin Resistance in Rodents.

Excess reactive oxygen species (ROS) generation and inflammation may contribute to obesity-associated skeletal muscle insulin resistance. Ghrelin is a gastric hormone whose unacylated form (UnAG) is associated with whole-body insulin sensitivity in humans and may reduce oxidative stress in nonmuscle cells in vitro. We hypothesized that UnAG 1) lowers muscle ROS production and inflammation and enhances tissue insulin action in lean rats and 2) prevents muscle metabolic alterations and normalizes insulin resistance and hyperglycemia in high-fat diet (HFD)-induced obesity. In 12-week-old lean rats, UnAG (4-day, twice-daily subcutaneous 200-µg injections) reduced gastrocnemius mitochondrial ROS generation and inflammatory cytokines while enhancing AKT-dependent signaling and insulin-stimulated glucose uptake. In HFD-treated mice, chronic UnAG overexpression prevented obesity-associated hyperglycemia and whole-body insulin resistance (insulin tolerance test) as well as muscle oxidative stress, inflammation, and altered insulin signaling. In myotubes, UnAG consistently lowered mitochondrial ROS production and enhanced insulin signaling, whereas UnAG effects were prevented by small interfering RNA-mediated silencing of the autophagy mediator ATG5. Thus, UnAG lowers mitochondrial ROS production and inflammation while enhancing insulin action in rodent skeletal muscle. In HFD-induced obesity, these effects prevent hyperglycemia and insulin resistance. Stimulated muscle autophagy could contribute to UnAG activities. These findings support UnAG as a therapeutic strategy for obesity-associated metabolic alterations.

Gastric bypass-induced weight loss alters obesity-associated patterns of plasma pentraxin-3 and systemic inflammatory markers.

BACKGROUND: Systemic inflammation contributes to obesity-associated complications. The short pentraxin C-reactive protein (CRP) is a validated inflammatory marker, whereas long pentraxin-3 (PTX3) limits inflammation and is adaptively stimulated by proinflammatory cytokines in vitro. Severely obese (SO) patients (body mass index [BMI]>40] have the highest obesity-associated complications and increasingly undergo surgical treatment. SO-associated changes in plasma PTX3 and their interactions with systemic inflammation are, however, unknown. OBJECTIVE: We sought to determine potential alterations in plasma PTX3 and their associations with changes in inflammatory markers before and after weight loss induced by laparoscopic Roux-en-Y gastric bypass (LRYGB). SETTING: University hospital in Trieste, Italy. METHODS: Plasma PTX3, CRP, and cytokines, including tumor necrosis factor α and interleukin 6 were measured in (1) 24 individuals with severe, class III obesity (SO; age = 42 ± 1 yr, female/male = 18/6, BMI = 45 ± 1 kg/m(2)) before and 3, 6, and 12 months after LRYGB; and (2) age- and sex-matched normal-weight (N; n = 56, BMI = 22 ± .2 kg/m(2)) or class I obese individuals (O; n = 44, BMI = 31.2 ± .3 kg/m(2)). RESULTS: SO, but not O, had higher plasma PTX3 compared with N, associated with highest proinflammatory cytokines and CRP (P<.05 versus N-O). In all patients, plasma interleukin 6 and tumor necrosis factor α were associated positively with PTX3 (P<.05). Plasma CRP and proinflammatory cytokines declined during LRYGB-induced weight loss. In contrast, high PTX3 further increased and remained elevated (P<.05 versus basal). CONCLUSIONS: Obesity level and energy balance modulate interactions between PTX3 and systemic inflammation. Elevated PTX3 is a novel, potentially adaptive alteration associated with proinflammatory cytokines in SO. Their differential changes conversely suggest circulating PTX3 as a novel negative inflammatory marker in SO undergoing LRYGB-induced weight loss.

Carnitine in maintenance hemodialysis patients.

Carnitine is a conditionally essential metabolite that plays a critical role in cell physiology. Carnitine is necessary for fatty acid transport to sites of beta-oxidation in the mitochondria, where it also helps to prevent organic acid accumulation. Because of these key regulatory functions, carnitine represents a crucial determinant of mitochondrial energy metabolism, whose deficiency may lead to metabolic and clinical disturbances. Loss of carnitine through dialytic membranes occurs in maintenance hemodialysis, resulting in potential carnitine depletion and relative increments of esterified carnitine forms. Carnitine supplementation has been reported to counteract some of these alterations and has been associated with some clinical benefits, such as enhanced response to erythropoietin as well as improvement in exercise tolerance, intradialytic symptom, hyperparathyroidism, insulin resistance, inflammatory and oxidant status, protein balance, lipid profile, cardiac function, and quality of life. Carnitine supplementation has an attractive theoretical rationale; however, there are no definitive supportive studies and conclusive evidence that L-carnitine supplementation in maintenance hemodialysis patients could improve these conditions. A trial of carnitine administration could be attempted for 6 to 12 months only in selected patients on dialysis who do not adequately respond to standard therapies, in the presence of symptomatology, and in conjunction with patient dialysis age and documented L-carnitine deficiency.

The association between hematological parameters and insulin resistance is modified by body mass index - results from the North-East Italy MoMa population study.

OBJECTIVE: Increments in red blood cell count (RBC), hemoglobin (Hb) and hematocrit (Ht) levels are reportedly associated with higher insulin resistance (IR). Obesity may cause IR, but underlying factors remain incompletely defined, and interactions between obesity, hematological parameters and IR are incompletely understood. We therefore determined whether: 1) BMI and obesity per se are independently associated with higher RBC, hemoglobin and hematocrit; 2) hematological parameters independently predict insulin resistance in obese individuals. DESIGN AND METHODS: We investigated the associations between BMI, hematological parameters and insulin resistance as reflected by homeostasis model assessment (HOMA) in a general population cohort from the North-East Italy MoMa epidemiological study (M/F = 865/971, age = 49 ± 1). RESULTS: In all subjects, age-, sex- and smoking-adjusted hematological parameters were positively associated with BMI in linear regression (P<0.05), but not after adjustment for HOMA or waist circumference (WC) and potential metabolic confounders. No associations were found between hematological parameters and BMI in lean, overweight or obese subgroups. Associations between hematological parameters and HOMA were conversely independent of BMI in all subjects and in lean and overweight subgroups (P<0.01), but not in obese subjects alone. CONCLUSIONS: In a North-East Italy general population cohort, obesity per se is not independently associated with altered RBC, Hb and Ht, and the association between BMI and hematological parameters is mediated by their associations with abdominal fat and insulin resistance markers. High hematological parameters could contribute to identify insulin resistance in non-obese individual, but they do not appear to be reliable insulin resistance biomarkers in obese subjects.

Acylated ghrelin limits fat accumulation and improves redox state and inflammation markers in the liver of high-fat-fed rats.

OBJECTIVE: Obesity commonly causes hepatic lipid accumulation that may favor oxidative stress and inflammation with negative clinical impact. Acylated ghrelin (A-Ghr) modulates body lipid distribution and metabolism, and it may exert antioxidant effects in vitro as well as systemic anti-inflammatory effects in vivo. The impact of A-Ghr on liver triglyceride content, redox state and inflammation markers in diet-induced obesity was investigated. DESIGN AND METHODS: A-Ghr (200-µg/injection: HFG) or saline (HF) were administered subcutaneously twice-daily for 4 days to 12-week-old male rats fed a high-fat diet for 1 month (n = 8-10/group). RESULTS: Compared to lean animals, liver triglyceride accumulation occurred in HF despite enhanced phosphorylation of the lipid oxidation regulator AMPK and preserved mitochondrial enzyme activities. High triglycerides were accompanied by pro-oxidant changes in redox state and proinflammatory changes in NF-kB and TNF-alpha. A-Ghr limited liver triglyceride excess (P < 0.05 HF > HFG > Control) with concomitant activation of glutathione peroxidase and normalized redox state and cytokines. A-Ghr-induced liver changes were associated with higher plasma adiponectin and lower circulating fatty acids (P < 0.05 HFG vs. HF) CONCLUSIONS: A-Ghr limits liver triglyceride accumulation and normalizes tissue redox state and inflammation markers in diet-induced obese rats. These results suggest a favorable impact of A-Ghr on hepatic complications of diet-induced obesity.

Obesity and high waist circumference are associated with low circulating pentraxin-3 in acute coronary syndrome.

BACKGROUND: Long pentraxin 3 (PTX3) is a component of the pentraxin superfamily and a potential marker of vascular damage and inflammation, associated with negative outcome in patients with acute coronary syndromes (ACS). Obesity is a risk factor for cardiovascular disease and PTX3 production is reported in abdominal adipose tissue. Low PTX3 is however reported in the obese population, and obesity per se may be associated with less negative ACS outcome. METHODS: We investigated the potential impact of obesity and high waist circumference (reflecting abdominal fat accumulation) on plasma PTX3 concentration in ACS patients (n = 72, 20 obese) compared to age-, sex- and BMI-matched non-ACS individuals. RESULTS: Both obese and non-obese ACS patients had higher PTX3 than matched non-ACS counterparts, but PTX3 was lower in obese than non-obese individuals in both groups (all P < 0.05). PTX3 was also lower in ACS subjects with high than in those with normal waist circumference (WC). Plasma PTX3 was accordingly associated negatively with BMI and WC, independently of age and plasma creatinine. No associations were observed between PTX3 and plasma insulin, glucose or the short pentraxin and validated inflammation marker C-reactive protein, that was higher in ACS than in non-ACS individuals independently of BMI or WC. CONCLUSIONS: Obesity is associated with low circulating PTX3 in ACS. This association is also observed in the presence of abdominal fat accumulation as reflected by elevated waist circumference. Low PTX3 is a novel potential modulator of tissue damage and outcome in obese ACS patients.

Gastric bypass does not normalize obesity-related changes in ghrelin profile and leads to higher acylated ghrelin fraction.

OBJECTIVE: Gastric bypass (GBP) lowers food intake, body weight, and insulin resistance in severe obesity (SO). Ghrelin is a gastric orexigenic and adipogenic hormone contributing to modulate energy balance and insulin action. Total plasma ghrelin (T-Ghr) level is low and inversely related to body weight and insulin resistance in moderately obese patients, but these observations may not extend to the orexigenic acylated form (A-Ghr) whose plasma concentration increase in moderate obesity. DESIGN AND METHODS: We investigated the impact of GBP on plasma T-, A-, and A/T-Ghr in SO patients (n = 28, 20 women), with measurements at baseline and 1, 3, 6, and 12 months after surgery. Additional cross-sectional comparison was performed between nonobese, moderately obese, and SO individuals before GBP and at the end of the follow-up period. RESULTS: Before GBP, SO had lowest T-Ghr and highest A/T-Ghr profile compared with both nonobese and moderately obese individuals. Lack of early (0-3 months from GBP) T-Ghr changes masked a sharp increase in A-Ghr and A/T-Ghr profile (P < 0.05) that remained elevated following later increments (6-12 months) of both T- and A-Ghr (P < 0.05). Levels of A-Ghr and A/T-Ghr at 12 months of follow-up remained higher than in matched moderately obese individuals not treated with surgery (P < 0.05). CONCLUSIONS: The data show that following GBP, early T-Ghr stability masks elevation of A/T-Ghr, that is stabilized after later increments of both T- and A-hormones. GBP does not normalize the obesity-associated elevated A/T-Ghr ratio, instead resulting in enhanced A-Ghr excess. Excess A-Ghr is unlikely to contribute to, and might limit, the common GBP-induced declines of appetite, body weight, and insulin resistance.

Adipokines, ghrelin and obesity-associated insulin resistance in nondiabetic patients with acute coronary syndrome.

Altered glucose metabolism negatively modulates outcome in acute coronary syndromes (ACS). Insulin resistance is commonly associated with increasing BMI in the general population and these associations may involve obesity-related changes in circulating ghrelin and adipokines. We aimed at investigating interactions between BMI, insulin resistance and ACS and their associations with plasma ghrelin and adipokine concentrations. Homeostasis model assessment of insulin resistance (HOMA(IR))-insulin resistance index, plasma adiponectin, leptin, total (T-Ghrelin), acylated (Acyl-Ghrelin), and desacylated ghrelin (Desacyl-Ghrelin) were measured in 60 nondiabetic ACS patients and 44 subjects without ACS matched for age, sex, and BMI. Compared with non-ACS, ACS patients had similar HOMA(IR) and plasma adipokines, but lower T- and Desacyl-Ghrelin and higher Acyl-Ghrelin. Obesity (BMI > 30) was associated with higher HOMA(IR), lower adiponectin, and higher leptin (P < 0.05) similarly in ACS and non-ACS subjects. In ACS (n = 60) HOMA(IR) remained associated negatively with adiponectin and positively with leptin independently of BMI and c-reactive protein (CRP) (P < 0.05). On the other hand, low T- and Desacyl-Ghrelin with high Acyl-Ghrelin characterized both obese and non-obese ACS patients and were not associated with HOMA(IR). In conclusion, in ACS patients, obesity and obesity-related changes in plasma leptin and adiponectin are associated with and likely contribute to negatively modulate insulin resistance. ACS per se does not however enhance the negative impact of obesity on insulin sensitivity. High acylated and low desacylated ghrelin characterize ACS patients independently of obesity, but are not associated with insulin sensitivity.

Ghrelin and muscle metabolism in chronic uremia.

Patients with chronic kidney disease (CKD) are prone to nutritional complications with negative prognostic impact. In particular, protein-energy wasting is a major CKD-associated clinical burden, and emerging evidence indicates that clustered metabolic alterations, including inflammation, oxidative stress, and insulin resistance, contribute to loss of skeletal muscle mass. Ghrelin is a gastric hormone discovered in its acylated form and extensively studied for its appetite-stimulating effect. Further studies have shown that ghrelin may positively modulate systemic inflammation and insulin action. In addition, a role of ghrelin in the regulation of redox state has been described in vitro. Ghrelin treatment could therefore represent a potential comprehensive therapeutic approach for CKD-related metabolic and nutritional complications, and evidence supporting this hypothesis has emerged in clinical and experimental CKD. Clinical trials of ghrelin administration are needed to test the hypothesis that ghrelin may chronically improve nutritional status and outcome in CKD patients.

High-fat diet with acyl-ghrelin treatment leads to weight gain with low inflammation, high oxidative capacity and normal triglycerides in rat muscle.

Obesity is associated with muscle lipid accumulation. Experimental models suggest that inflammatory cytokines, low mitochondrial oxidative capacity and paradoxically high insulin signaling activation favor this alteration. The gastric orexigenic hormone acylated ghrelin (A-Ghr) has antiinflammatory effects in vitro and it lowers muscle triglycerides while modulating mitochondrial oxidative capacity in lean rodents. We tested the hypothesis that A-Ghr treatment in high-fat feeding results in a model of weight gain characterized by low muscle inflammation and triglycerides with high muscle mitochondrial oxidative capacity. A-Ghr at a non-orexigenic dose (HFG: twice-daily 200-µg s.c.) or saline (HF) were administered for 4 days to rats fed a high-fat diet for one month. Compared to lean control (C) HF had higher body weight and plasma free fatty acids (FFA), and HFG partially prevented FFA elevation (P<0.05). HFG also had the lowest muscle inflammation (nuclear NFkB, tissue TNF-alpha) with mitochondrial enzyme activities higher than C (P<0.05 vs C, P = NS vs HF). Under these conditions HFG prevented the HF-associated muscle triglyceride accumulation (P<0.05). The above effects were independent of changes in redox state (total-oxidized glutathione, glutathione peroxidase activity) and were not associated with changes in phosphorylation of AKT and selected AKT targets. Ghrelin administration following high-fat feeding results in a novel model of weight gain with low inflammation, high mitochondrial enzyme activities and normalized triglycerides in skeletal muscle. These effects are independent of changes in tissue redox state and insulin signaling, and they suggest a potential positive metabolic impact of ghrelin in fat-induced obesity.

High plasma retinol binding protein 4 (RBP4) is associated with systemic inflammation independently of low RBP4 adipose expression and is normalized by transplantation in nonobese, nondiabetic patients with chronic kidney disease.

OBJECTIVE: Adipose-secreted retinol binding protein 4 (RBP4) circulates in free (active) and transthyretin (TTR)-bound forms and may be associated with obesity-related inflammation. Potential involvement of plasma and adipose RBP4 in systemic inflammation in the absence of obesity and diabetes is unknown. Inflammation reduces survival in chronic kidney disease (CKD) [particularly in maintenance haemodialysis (MHD)], and plasma RBP4 may increase with renal dysfunction. We investigated (i) potential associations between RBP4 and inflammation in CKD and (ii) the role of adipose tissue in this putative interaction. DESIGN: Cross-sectional. PATIENTS: Nonobese, nondiabetic patients with CKD undergoing conservative (CT: n = 10) or MHD treatment (n = 25) and healthy control subjects (C: n = 11). Renal transplant recipients (n = 5) were studied to further assess the impact of restored near-normal renal function. MEASUREMENTS: Plasma RBP4, TTR and C-reactive protein (CRP), adipose RBP4 expression. RESULTS: Plasma RBP4, TTR and CRP were highest in MHD (P < 0·05). Adipose RBP4 mRNA was, however, comparably low in CT and MHD (P < 0·05 vs C), and all parameters were normalized in transplant recipients (P < 0·05 vs MHD). In all subjects (n = 51), creatinine and TTR (P < 0·05) but not adipose RBP4 mRNA were associated with plasma RBP4. Plasma RBP4 but not its adipose expression was in turn associated positively (P < 0·05) with CRP independently of creatinine-TTR. CONCLUSIONS: High plasma RBP4 and inflammation are clustered in CKD in the absence of obesity and diabetes and are normalized by transplantation. Adipose RBP4 expression is not involved in plasma RBP4 elevation, which appears to be mainly because of passive accumulation, or in CKD-associated inflammation.

Hemodialysis induces p66(shc) gene expression in nondiabetic humans: correlations with oxidative stress and systemic inflammation.

OBJECTIVE: Oxidative stress and inflammation characterize hemodialysis (HD) and are associated with malnutrition, cardiovascular disease, and poor clinical outcome. p66(shc) stimulates oxidative stress and atherogenesis. The objective of the present study was to assess p66(shc) expression levels in HD and their associations with inflammatory and oxidative stress markers. DESIGN: p66(shc) messenger ribonucleic acid (mRNA) was compared with systemic oxidative stress and inflammation markers in control subjects and patients on HD before and after a single HD session in a cross-sectional analysis. SETTING: Outpatient hemodialysis unit. PATIENTS: The study included stable HD patients (n = 21, men/women: 18/3) who were on HD 3 times per week for a minimum of 8 weeks; age-matched control subjects (n = 22, men/women:17/5). MAIN OUTCOME MEASURE: mRNA levels of p66(shc), tumor necrosis factor α (TNF-α), and pentraxin 3 (PTX3), p66(shc) protein levels in white blood cells, lipid peroxidation (in the form of plasma thiobarbituric acid-reactive substance [TBARS]) and serum C-reactive protein. RESULTS: In patients on dialysis, of the p66(shc), TNF-α, and PTX3 mRNAs, p66(shc) protein levels were higher (P < .05) than in control subjects, as well as plasma TBARS and C-reactive protein (P < .05). p66(shc) mRNA directly correlated with TBARS (r = 0.69, P = .0005) and with TNF-α mRNA (r = 0.63, P = .003). These associations were confirmed in the whole study population (TBARS: r = 0.541, P = .0003; TNF-α: r = 0.581, P < .0001), whereas in the control group only the positive association between p66(shc) and TNF-α was detected. TNF-α was directly correlated with PTX3 both in HD patients (r = 0.72, P = .0005) and in the whole study group (r = 0.678, P < .0001). The dialysis session affected neither p66(shc) and TNF-α mRNA nor p66(shc) protein expression, whereas it further increased (P = .002) PTX3 mRNA. As compared with predialysis levels, TBARS were reduced (P < .05) after dialysis. In these conditions, p66(shc) remained directly correlated with TNF-α (r = 0.901, P < .0001). CONCLUSIONS: Increased p66(shc) gene expression correlates with TNF-α mRNA and with levels of markers of oxidative stress in HD. We suggest a novel link between HD-associated inflammation and p66(shc) gene expression contributing to systemic oxidative stress.

Fighting protein-energy wasting in chronic kidney disease: a challenge of complexity.

Chronic uremia is often characterized by wasting of muscle and fat mass, which has been defined as protein-energy wasting (PEW), and is responsible for substantial worsening of patient outcome in terms of morbidity and mortality, mostly from cardiovascular events. Despite major advances in patient treatment, nutritional outcome in patients with end-stage renal disease has not improved substantially in recent years. Extensive research in this field has provided plausible explanations for this limitation by indicating that the pathogenesis of PEW in kidney disease is complex and multifactorial. Complexity involves underlying metabolic alterations, including inflammation, oxidative stress, and insulin resistance. In addition, patient heterogeneity is increasing with large numbers of obese individuals as a result of the ongoing obesity epidemics. Several tissues are involved in cross-talk and contribute to metabolic derangements, including adipose tissue, the gut, and the central nervous system, with novel mediators including the gastric hormone ghrelin. Acknowledging its complex pathogenesis may favor the development of novel and more effective therapeutic tools for PEW. These should ideally be effective in treating the underlying common mechanisms of wasting, which appear to include oxidative stress, inflammation, and insulin resistance.

Complete correction of anemia by erythropoiesis-stimulating agents is associated with insulin resistance in hemodialysis patients.

Insulin resistance and anemia secondary to erythropoietin deficiency characterize patients with end-stage kidney disease. In a cross-sectional analysis, we examined the relationship between erythropoietin-mediated correction of anemia and insulin sensitivity in nondiabetic hemodialysis patients. Insulin sensitivity (euglycemic-hyperinsulinemic clamp) and endogenous glucose production (primed-continuous infusion of [6,6-(2)H(2)]glucose) were determined in two groups of patients with normal hemoglobin (n:8; mean hemoglobin: 14.0 ± 0.3 g/dl) or with mild anemia (n:10; mean hemoglobin: 12.1 ± 0.9 g/dl). The patients with normal hemoglobin were receiving higher (P < 0.05) erythropoietin doses than those with mild anemia (171 ± 73 and 91 ± 39 U kg(-1) wk(-1), respectively). The two groups were matched for all other potential determinants of insulin resistance. Endogenous glucose production was similar in the two groups of patients in the postabsorptive state and was completely suppressed by insulin infusion. During the hyperinsulinemic clamp, the rate of glucose infusion to maintain euglycemia was significantly lower (P < 0.01) in the patients with normal hemoglobin levels [166 ± 31 mg (m(2))(-1) min(-1)] than in those with mild anemia [251 ± 49 mg (m(2))(-1) min(-1)] and in a group of matched controls [275 ± 68 mg (m(2))(-1) min(-1)]. In pooled patients, individual values of hemoglobin concentrations inversely correlated with the rates of insulin-mediated glucose infusion, both as absolute values (r = -0.58; P < 0.05) and as values normalized by steady-state plasma insulin concentration (r = -0.74; P < 0.001). In conclusion, this exploratory study indicates that complete correction of anemia by erythropoietin treatment in patients with end-stage kidney disease on hemodialysis is associated with impaired insulin sensitivity.

Insulin downregulates SIRT1 and AMPK activation and is associated with changes in liver fat, but not in inflammation and mitochondrial oxidative capacity, in streptozotocin-diabetic rat.

BACKGROUND & AIMS: Involvement of insulin in diabetes-associated liver triglyceride deposition and its potential pathways remain incompletely defined. SIRT1 may negatively modulate lipogenesis and liver triglyceride accumulation, involving AMP-activated protein kinase (AMPK) activation. In streptozotocin-diabetic rats, we hypothesized that insulin negatively modulates liver SIRT1 and activates AMPK-inhibited lipogenic mediators leading to triglyceride accumulation. The impact of insulin deprivation (INS-) and replacement (INS+) on liver inflammation and mitochondrial oxidative capacity (also potentially regulating triglyceride deposition) was also measured. METHODS: Streptozotocin-diabetic rats under chronic (8-week) INS- and INS+. RESULTS: Compared to INS- (P < 0.05), INS+ had low liver SIRT1 with low AMPK activating phosphorylation, low inactivating phosphorylation of its lipogenic target acetyl-CoA carboxylase and high tissue triglycerides. INS- (P < 0.05 vs Control) had liver inflammation and high mitochondrial oxidative capacity, but neither was modulated by INS+. Pair-feeding showed no influence of spontaneous overeating on insulin-induced changes. CONCLUSIONS: Insulin replacement downregulates SIRT1 and AMPK activation in vivo in streptozotocin-diabetic rat liver, likely contributing to insulin-induced liver triglyceride accumulation. Under the current experimental conditions, insulin-deprived diabetes is associated with liver inflammation and high mitochondrial oxidative capacity, that are not affected by insulin replacement and are therefore unlikely to contribute to tissue triglyceride changes in this model.

Metabolic syndrome and chronic kidney disease.

Obesity is a global health threat because of its associated metabolic and cardiovascular complications. Metabolic and hemodynamic complications of obesity (insulin resistance and hyperglycemia, hypertension, atherogenic dyslipidemia) are often clustered in the metabolic syndrome, leading to high cardiovascular morbidity and mortality. In recent years, epidemiological studies have clearly indicated that both obesity and the metabolic syndrome are independent risk factors for chronic kidney disease and these associations are at least in part independent of diabetes and hypertension per se. Additional mechanisms associated with obesity and metabolic syndrome leading to reduced renal function may include altered levels of adipose tissue hormones, inflammation, and oxidative stress. The ongoing worldwide obesity epidemic is therefore likely to increase the number of patients with chronic uremia and features of the metabolic syndrome in the next few years. Moreover, the onset and maintenance of renal damage may worsen metabolic syndrome features including insulin resistance and hypertension, leading to potential vicious cycles with negative clinical effect. Further understanding of the interactions between obesity, metabolic syndrome, and chronic kidney disease represents a potential strategy to design more effective treatments aimed at reducing morbidity and mortality in uremic patients.