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.

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.

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.

Insulin resistance in chronic uremia.

Insulin resistance often characterizes chronic uremia, and is associated with enhanced morbidity and mortality, because it may contribute to protein-energy wasting (in turn, an independent predictor of reduced survival), atherosclerosis, and cardiovascular death. Causes of insulin resistance in chronic uremia are complex and multifactorial. Obesity is emerging as an independent risk factor for chronic kidney disease, and an expected rise in number of obese uremic patients because of the ongoing worldwide obesity epidemic is likely to increase the prevalence of insulin resistance in chronic uremia in the near future. Similar to the general population, reported associations between obesity and insulin resistance in chronic uremia support a role of adipose tissue and altered adipokine profiles in insulin resistance in obese chronic kidney disease patients. Hormonal imbalances, chronic acidosis, and systemic inflammation and oxidative stress are uremia-associated relevant causes of insulin resistance in nonobese individuals. A further understanding of the causes of insulin resistance in chronic uremia represents a potential important tool in the design of more effective therapeutic strategies to reduce uremia-associated morbidity and mortality.

Ghrelin enhances in vivo skeletal muscle but not liver AKT signaling in rats.

OBJECTIVE: Ghrelin administration can induce fat weight gain and hyperglycemia (potentially through ghrelin-induced hepatic glucose production), but plasma ghrelin is positively associated with whole-body insulin sensitivity (mainly reflecting muscle insulin action) being increased in lean individuals or after diet-induced weight loss and reduced in obesity or after diet-induced weight gain. To investigate potential mechanisms, we measured in vivo effects of sustained ghrelin administration at a non-orexigenic dose on skeletal muscle and liver insulin signaling at the AKT level and adipokine expression changes. RESEARCH METHODS AND PROCEDURES: Young-adult male rats received 4-day, twice daily subcutaneous ghrelin (200 mug/injection) or saline. We measured skeletal muscle (mixed, gastrocnemius; oxidative, soleus) and liver protein levels of activated [phosphorylated (P)] and total (T) AKT and glycogen synthase kinase (GSK; reflecting AKT-dependent GSK inactivation) and epididymal adipose tissue adipokine mRNA. RESULTS: Ghrelin increased body weight (+1.4%) and blood glucose (both p < 0.05 vs. saline) but not food intake, plasma insulin, or free fatty acids. Ghrelin, however, enhanced P/T/AKT and P/T/GSK ratios and glucose transporter-4 mRNA in soleus (p < 0.05), but not in gastrocnemius, muscle. In contrast, ghrelin reduced hepatic P/T-AKT and P/T-GSK. No alterations occurred in adiponectin, leptin, or resistin transcripts or plasma adiponectin. DISCUSSION: Despite moderate weight gain and in the absence of insulin-free fatty acid changes, sustained ghrelin administration enhanced oxidative muscle AKT activation. Reduced liver AKT signaling could potentially contribute to concomitant blood glucose increments. These findings support ghrelin as a novel tissue-specific modulator of lean tissue AKT signaling with insulin-sensitizing effects in skeletal muscle but not in liver in vivo.

Glomerular permeability defect in hypertension is dependent on renin angiotensin system activation.

BACKGROUND: The aim of the present study was to compare glomerular permeability alterations associated with experimental hypertension models known to have different effects on the circulating renin-angiotensin system (RAS). METHODS: Five groups, 10 animals each, were studied. One group served as a nonhypertensive control. The other four groups of hypertensive animals were composed of spontaneously hypertensive rats, deoxycorticosterone acetate hypertensive rats, Goldblatt two-kidney, one-clip rats, and a group of Wistar rats infused with angiotensin II (200 ng/kg/min). Tail-cuff sphygmomanometric systolic blood pressure (BP), albumin permeability determined in isolated glomeruli exposed to oncotic gradients (P(alb)), glomerular filtration rate (GFR, iopamidol method), plasma renin activity (PRA), and albuminuria were evaluated. RESULTS: Alterations in P(alb) and albumin excretion rate were more evident in the experimental models with an activation of the RAS despite similar levels of systolic BP and GFR. A positive correlation was found between P(alb) and albuminuria (r = 0.51; P < .001) and between systolic BP and albuminuria (r = 0.37; P < .01). No relation was found between systolic BP and P(alb). CONCLUSIONS: The present study indicates that the activation of the RAS plays a significant role in the development of glomerular albumin permeability defects in hypertensive models and may contribute to the mechanisms that lead to target organ damage in hypertension.

Genetic polymorphisms of the renin-angiotensin-aldosterone system and renal insufficiency in essential hypertension.

OBJECTIVE: The renin-angiotensin-aldosterone system (RAAS) plays an important role in the control of renal function both in physiological and pathological conditions. The aim of the present study was to evaluate the relation between four genetic polymorphisms of the RAAS and renal insufficiency in a population of patients with essential hypertension living in north-east Italy. DESIGN AND METHODS: Eighty-six hypertensive patients with renal insufficiency and 172 hypertensive patients without renal damage matched for age and hypertension duration to within 2 years were evaluated. Genotyping for insertion/deletion of angiotensin-converting enzyme (ACE I/D), angiotensinogen (AGT) M235T, angiotensin II type 1 receptor (AT1R) A1166C and aldosterone synthase (CYP11B2) -344C/T polymorphisms were performed using polymerase chain reaction, with further restriction analysis when required. RESULTS: Each of the genetic polymorphisms of the RAAS genes was associated with renal failure; the adjusted odds ratios were 1.47 and 1.89 for ACE D allele, assuming a co dominant and a recessive mode of inheritance, respectively; 1.51 for AGT T235 allele assuming a co dominant, and 1.98 assuming a recessive, pattern of inheritance; 1.79 for AT1R C1166 allele considering a dominant pattern; and 3.89 for CYP11B2 -344C allele as a recessive effect. However, CYP11B2 genotypes were not in Hardy-Weinberg equilibrium among controls. The associations AGT TT-AT1R AC and CYP11B2 CC-ACE DD showed a possible positive interaction in the development of renal insufficiency among hypertensive subjects. The association AGT MM-AT1R AA and AGT MM-AT1R AA-CYP11B2 TT or TC combinations were associated with a reduced risk for renal failure. CONCLUSIONS: Our findings suggest that in patients with essential hypertension an unfavorable genetic pattern of RAAS may contribute to the increased risk for the development of renal failure.

Ghrelin regulates mitochondrial-lipid metabolism gene expression and tissue fat distribution in liver and skeletal muscle.

Ghrelin is a gastric hormone increased during caloric restriction and fat depletion. A role of ghrelin in the regulation of lipid and energy metabolism is suggested by fat gain independent of changes in food intake during exogenous ghrelin administration in rodents. We investigated the potential effects of peripheral ghrelin administration (two times daily 200-micrograms [DOSAGE ERROR CORRECTED] sc injection for 4 days) on triglyceride content and mitochondrial and lipid metabolism gene expression in rat liver and muscles. Compared with vehicle, ghrelin increased body weight but not food intake and circulating insulin. In liver, ghrelin induced a lipogenic and glucogenic pattern of gene expression and increased triglyceride content while reducing activated (phosphorylated) stimulator of fatty acid oxidation, AMP-activated protein kinase (AMPK, all P < 0.05), with unchanged mitochondrial oxidative enzyme activities. In contrast, triglyceride content was reduced (P < 0.05) after ghrelin administration in mixed (gastrocnemius) and unchanged in oxidative (soleus) muscle. In mixed muscle, ghrelin increased (P < 0.05) mitochondrial oxidative enzyme activities independent of changes in expression of fat metabolism genes and phosphorylated AMPK. Expression of peroxisome proliferator-activated receptor-gamma, the activation of which reduces muscle fat content, was selectively increased in mixed muscle where it paralleled changes in oxidative capacities (P < 0.05). Thus ghrelin induces tissue-specific changes in mitochondrial and lipid metabolism gene expression and favors triglyceride deposition in liver over skeletal muscle. These novel effects of ghrelin in the regulation of lean tissue fat distribution and metabolism could contribute to metabolic adaptation to caloric restriction and loss of body fat.