Deletion of ghrelin prevents aging-associated obesity and muscle dysfunction without affecting longevity.

During aging, decreases in energy expenditure and locomotor activity lead to body weight and fat gain. Aging is also associated with decreases in muscle strength and endurance leading to functional decline. Here, we show that lifelong deletion of ghrelin prevents development of obesity associated with aging by modulating food intake and energy expenditure. Ghrelin deletion also attenuated the decrease in phosphorylated adenosine monophosphate-activated protein kinase (pAMPK) and downstream mediators in muscle, and increased the number of type IIa (fatigue resistant, oxidative) muscle fibers, preventing the decline in muscle strength and endurance seen with aging. Longevity was not affected by ghrelin deletion. Treatment of old mice with pharmacologic doses of ghrelin increased food intake, body weight, and muscle strength in both ghrelin wild-type and knockout mice. These findings highlight the relevance of ghrelin during aging and identify a novel AMPK-dependent mechanism for ghrelin action in muscle.

Ghrelin prevents tumour- and cisplatin-induced muscle wasting: characterization of multiple mechanisms involved.

BACKGROUND: Cachexia and muscle atrophy are common consequences of cancer and chemotherapy administration. The novel hormone ghrelin has been proposed as a treatment for this condition. Increases in food intake and direct effects on muscle proteolysis and protein synthesis are likely to mediate these effects, but the pathways leading to these events are not well understood. METHODS: We characterized molecular pathways involved in muscle atrophy induced by Lewis lung carcinoma (LLC) tumour implantation in c57/bl6 adult male mice and by administration of the chemotherapeutic agent cisplatin in mice and in C2C12 myotubes. The effects of exogenous ghrelin administration and its mechanisms of action were examined in these settings. RESULTS: Tumour implantation and cisplatin induced muscle atrophy by activating pro-inflammatory cytokines, p38-C/EBP-ß, and myostatin, and by down-regulating Akt, myoD, and myogenin, leading to activation of ubiquitin-proteasome-mediated proteolysis and muscle weakness. Tumour implantation also increased mortality. In vitro, cisplatin up-regulated myostatin and atrogin-1 by activating C/EBP-ß and FoxO1/3. Ghrelin prevented these changes in vivo and in vitro, significantly increasing muscle mass (P < 0.05 for LLC and P < 0.01 for cisplatin models) and grip strength (P = 0.038 for LLC and P = 0.001 for cisplatin models) and improving survival (P = 0.021 for LLC model). CONCLUSION: Ghrelin prevents muscle atrophy by down-regulating inflammation, p38/C/EBP-ß/myostatin, and activating Akt, myogenin, and myoD. These changes appear, at least in part, to target muscle cells directly. Ghrelin administration in this setting is associated with improved muscle strength and survival.

Circulating inflammatory cytokines and adipokines are associated with increased risk of Barrett's esophagus: a case-control study.

BACKGROUND & AIMS: Obesity is associated with Barrett's esophagus (BE) and with changes in circulating levels of adipokines (leptin and adiponectin) and cytokines. Although studies have reported that adipokines and inflammatory cytokines are necessary for the development of BE, their role is controversial. METHODS: We performed a case-control study; cases (n = 141) were patients who underwent esophagogastroduodenoscopy and were found to have BE, which was based on endoscopy and histology, and controls (n = 139) were primary care patients eligible for screening colonoscopies who agreed to undergo esophagogastroduodenoscopy. We examined the association between BE and circulating levels of adipokines and cytokines (interleukin [IL]-1ß, IL-6, IL-8, IL-10, and IL-12p70; tumor necrosis factor-α; and interferon-γ). Cases and controls were compared by calculating odds ratios (ORs) and 95% confidence intervals (CIs) and using unadjusted and multiple logistic regression, adjusting for age, sex, race, waist-hip ratio, use of proton pump inhibitors and nonsteroidal anti-inflammatory drugs, and Helicobacter pylori infection. RESULTS: The adjusted ORs for BE were 2.62 (95% CI, 1.0-6.8), 5.18 (95% CI, 1.7-15.7), and 8.02 (95% CI, 2.79-23.07) for the highest quintile vs the lowest quintile of levels of IL-12p70, IL-8, and leptin, respectively, but the OR was not significant for IL-6 (2.39; 95% CI, 0.84-6.79). The adjusted OR for BE was 0.14 for highest quintile of IL-10 compared with lowest quintile (95% CI, 0.05-0.35) and 0.03 for IL-1ß ≥ median vs none detected (95% CI, 0.006-0.13). Higher levels of IL-8 and leptin and lower levels of IL-10 and IL-1ß were associated with the presence of long-segment (≥3 cm) and short-segment BE. There were no differences between cases and controls in levels of interferon-γ, tumor necrosis factor-α, adiponectin, or insulin. CONCLUSIONS: BE is associated with circulating inflammatory cytokines and leptin and low levels of anti-inflammatory cytokines. These findings could partly explain the effect of obesity on BE.

The role of ghrelin in anorexia-cachexia syndromes.

Anorexia, sarcopenia, and cachexia are common complications of many chronic conditions including cancer, rheumatoid arthritis, HIV infection, aging, and chronic lung, heart, or kidney disease. Currently, there is no effective treatment for muscle atrophy or wasting conditions although they typically take a significant toll on the quality of life of patients and are associated with poor prognosis and decreased survival. Ghrelin affects multiple key pathways in the regulation of body weight, body composition, and appetite in the setting of cachexia that may lead to an increase in appetite and growth hormone secretion and a reduction in energy expenditure and inflammation. The net effect is increased lean body mass and fat mass preservation. In this chapter, we review the mechanisms of action of ghrelin and present the available data in animal models and human trials using ghrelin or ghrelin mimetics in different settings of cachexia.

Renal plasma flow: glomerular filtration rate relationships in man during direct renin inhibition with aliskiren.

We examined the relation between change in renal plasma flow (RPF) and change in glomerular filtration rate (GFR) in healthy humans on a low-salt diet during direct renin inhibition with aliskiren. We measured the renal hemodynamic response to acute dosing of 300mg aliskiren by mouth to 19 healthy normotensive subjects (age, 33+/-3 years; baseline RPF, 575+/-23; GFR, 138+/-14mL/min/1.73m(2)) on a low-sodium diet (10mmol/day). GFR and RPF were measured by the clearance of inulin and para-aminohippurate. There was a marked increase in average RPF (169+/-24mL/min/1.73m(2)) and a small rise in average GFR (1.4+/-5mL/min/1.73m(2)) from baseline in response to aliskiren. There was a clear correlation between the change in RPF and the change in GFR between subjects (r=0.65; P < .003). A substantial increase in RPF was accompanied by a rise in GFR. Dependence of GFR on RPF was identified in healthy humans after RPF rose significantly with aliskiren. The responsible mechanism likely involves intravascular oncotic pressure along the glomerular capillary resulting in greater surface area available for filtration.