Whi2 is a conserved negative regulator of TORC1 in response to low amino acids.

Yeast WHI2 was originally identified in a genetic screen for regulators of cell cycle arrest and later suggested to function in general stress responses. However, the function of Whi2 is unknown. Whi2 has predicted structure and sequence similarity to human KCTD family proteins, which have been implicated in several cancers and are causally associated with neurological disorders but are largely uncharacterized. The identification of conserved functions between these yeast and human proteins may provide insight into disease mechanisms. We report that yeast WHI2 is a new negative regulator of TORC1 required to suppress TORC1 activity and cell growth specifically in response to low amino acids. In contrast to current opinion, WHI2 is dispensable for TORC1 inhibition in low glucose. The only widely conserved mechanism that actively suppresses both yeast and mammalian TORC1 specifically in response to low amino acids is the conserved SEACIT/GATOR1 complex that inactivates the TORC1-activating RAG-like GTPases. Unexpectedly, Whi2 acts independently and simultaneously with these established GATOR1-like Npr2-Npr3-Iml1 and RAG-like Gtr1-Gtr2 complexes, and also acts independently of the PKA pathway. Instead, Whi2 inhibits TORC1 activity through its binding partners, protein phosphatases Psr1 and Psr2, which were previously thought to only regulate amino acid levels downstream of TORC1. Furthermore, the ability to suppress TORC1 is conserved in the SKP1/BTB/POZ domain-containing, Whi2-like human protein KCTD11 but not other KCTD family members tested.

Genome-wide consequences of deleting any single gene.

Loss or duplication of chromosome segments can lead to further genomic changes associated with cancer. However, it is not known whether only a select subset of genes is responsible for driving further changes. To determine whether perturbation of any given gene in a genome suffices to drive subsequent genetic changes, we analyzed the yeast knockout collection for secondary mutations of functional consequence. Unlike wild-type, most gene knockout strains were found to have one additional mutant gene affecting nutrient responses and/or heat-stress-induced cell death. Moreover, independent knockouts of the same gene often evolved mutations in the same secondary gene. Genome sequencing identified acquired mutations in several human tumor suppressor homologs. Thus, mutation of any single gene may cause a genomic imbalance, with consequences sufficient to drive adaptive genetic changes. This complicates genetic analyses but is a logical consequence of losing a functional unit originally acquired under pressure during evolution.

Bcl-xL regulates mitochondrial energetics by stabilizing the inner membrane potential.

Mammalian Bcl-x(L) protein localizes to the outer mitochondrial membrane, where it inhibits apoptosis by binding Bax and inhibiting Bax-induced outer membrane permeabilization. Contrary to expectation, we found by electron microscopy and biochemical approaches that endogenous Bcl-x(L) also localized to inner mitochondrial cristae. Two-photon microscopy of cultured neurons revealed large fluctuations in inner mitochondrial membrane potential when Bcl-x(L) was genetically deleted or pharmacologically inhibited, indicating increased total ion flux into and out of mitochondria. Computational, biochemical, and genetic evidence indicated that Bcl-x(L) reduces futile ion flux across the inner mitochondrial membrane to prevent a wasteful drain on cellular resources, thereby preventing an energetic crisis during stress. Given that F(1)F(O)-ATP synthase directly affects mitochondrial membrane potential and having identified the mitochondrial ATP synthase ß subunit in a screen for Bcl-x(L)-binding partners, we tested and found that Bcl-x(L) failed to protect ß subunit-deficient yeast. Thus, by bolstering mitochondrial energetic capacity, Bcl-x(L) may contribute importantly to cell survival independently of other Bcl-2 family proteins.

Low total plasma carotenoids are independent predictors of mortality among older persons: the InCHIANTI study.

BACKGROUND: Plasma carotenoids are considered a valid biological marker for fruit and vegetable dietary intake. Recent studies show that low carotenoid levels are associated with a high risk of inflammation, cancer, and cardiovascular disease. AIM OF THE STUDY: To determine whether low plasma carotenoids are associated with increased mortality among older adults. METHODS: Longitudinal study among 1,043 adults, 65 years and older, in the InCHIANTI study, a population-based cohort of adults living in the community in the Tuscany region, Italy. RESULTS: Mean total carotenoid concentration was 1.80 micromol/l. During eight years of follow-up, 310 (29.7%) of participants died. Eight-year survival was lower in the lowest compared with the highest tertile of total serum carotenoids (P < 0.0001 by Mantel-Haenszel chi-square). In a multivariate Cox proportional hazards model adjusted for age, education, smoking, body mass index, energy intake, and chronic diseases, adults in the highest tertile of plasma carotenoids at enrollment had lower mortality compared to those in the lowest tertile (Hazards Ratio obtained by considering carotenoids level as an ordinal variable 0.81, 95%; CI 0.65-0.99; P for trend = 0.046). CONCLUSIONS: Low plasma carotenoids are an independent risk factor for mortality among older adults living in the community.

Carotenoids as protection against disability in older persons.

The purpose was to examine the relationship of total plasma carotenoids, an indicator of fruit and vegetable intake, with walking speed and severe walking disability in older adults. Nine hundred twenty-eight men and women aged 65 to 102 years from the Invecchiare in Chianti (Aging in the Chianti Area [InCHIANTI]) study, a population-based cohort in Tuscany, Italy, were studied. Plasma carotenoids were measured at enrollment (1998-2000), and walking speed over 4 meters and 400 meters distance were assessed at enrollment and 6 years later (2004-2006). At enrollment, 85 of 928 (9.2%) participants had severe walking disability (defined as being unable to walk or having a walking speed at the 4-meter walking test < 0.4 m/sec). After adjusting for potential confounders, participants with high total plasma carotenoids were significantly less likely to have prevalent severe walking disability (odds ration [OR] 0.59, 95% confidence interval [CI] 0.38-0.90, p = 0.01) and had higher walking speed over 4 meters (beta = 0.024, standard error [SE] = 0.011, p = 0.03) and over 400 meters (beta = 0.019, SE = 0.010, p = 0.04). Of 621 participants without severe walking disability at enrollment who were seen 6 years later, 68 (11.0%) developed severe walking disability. After adjusting for potential confounders, higher total plasma carotenoids were associated with a significantly lower risk of developing severe walking disability (OR 0.51, 95% CI 0.30-0.86, p = 0.01) and were associated with a less steep decline in 4-meter walking speed over a 6-year follow-up (n = 579; beta = 0.026, SE = 0.012, p = 0.03) and with lower incidence rates of being unable to successfully complete the 400-meter walking test at the 6-year follow-up visit (beta = -0.054, SE = 0.03, p = 0.04). High plasma carotenoids concentrations may be protective against the decline in walking speed and the development of severe walking disability in older adults.

Low plasma carotenoids and skeletal muscle strength decline over 6 years.

BACKGROUND: Higher intake of fruits and vegetables appears to protect against inflammation, poor physical performance, and disability, but its relationship with muscle strength is unclear. We examined the association between total plasma carotenoids, an indicator of fruit and vegetable intake, and changes in muscle strength over a 6-year follow-up in the participants aged 65 years and older in the InCHIANTI study, a population-based study in Tuscany, Italy. METHODS: Plasma carotenoids were measured at enrollment (1998-2000). Hip, knee, and grip strength were measured at enrollment and 6 years later (2004-2006) in 628 of the 948 participants evaluated at baseline. Poor muscle strength was defined as the lowest sex-specific quartile of hip, knee, and grip strength at enrollment. The main outcome was poor muscle strength at the 6-year follow-up visit among those participants originally in the upper three quartiles of strength at enrollment. RESULTS: Overall, 24.9% (110/441), 25.0% (111/444), and 24.9% (118/474) participants developed poor hip, knee, and grip strength, respectively. After adjusting for potential confounders, participants in the lowest versus the highest quartile of total plasma carotenoids at enrollment were at higher risk of developing poor hip (odds ratio [OR] = 3.01, 95% CI, 1.43-6.31, p =.004), knee (OR = 2.89, 95% CI, 1.38-6.02, p =.005), and grip (OR = 1.88, 95% CI, 0.93-3.56, p =.07) muscle strength at the 6-year follow-up visit. CONCLUSION: These findings suggest that older community-dwelling adults with lower plasma carotenoids levels, a marker of poor fruit and vegetable intake, are at a higher risk of decline in skeletal muscle strength over time.

Oxidative protein damage is associated with elevated serum interleukin-6 levels among older moderately to severely disabled women living in the community.

BACKGROUND: Elevated interleukin (IL)-6 is associated with adverse outcomes. Our objective was to determine whether serum protein carbonyls, an indicator of oxidative protein damage and oxidative stress, were associated with IL-6. METHODS: Serum protein carbonyls and IL-6 were measured in 739 women, age > or =65 years, in the Women's Health and Aging Study I. RESULTS: Geometric mean of protein carbonyls was 0.082 nmol/mg. After adjusting for age and smoking status, log(e) serum protein carbonyls were associated with log(e) IL-6 (beta = 0.143, standard error [SE] = 0.048, p =.003) in linear regression analyses and with elevated IL-6 (> or =2.5 pg/mL) (odds ratio = 1.38, 95% confidence interval, 1.02-1.86, p =.037) in logistic regression analyses. CONCLUSION. Oxidative damage to proteins is independently associated with serum IL-6 among older women living in the community. Increased oxidative stress may be a factor involved in the pathogenesis of the proinflammatory state that occurs in older adults.