Ikuo Nakamichi

Targeted disruption of Skp2 results in accumulation of cyclin E and p27Kip1, polyploidy and centrosome overduplication

The ubiquitin–proteasome pathway plays an important role in control of the abundance of cell cycle regulators. Mice lacking Skp2, an F‐box protein and substrate recognition component of an Skp1–Cullin–F‐box protein (SCF) ubiquitin ligase, were generated. Although Skp2−/− animals are viable, cells in the mutant mice contain markedly enlarged nuclei with polyploidy and multiple centrosomes, and show a reduced growth rate and increased apoptosis. Skp2−/− cells also exhibit increased accumulation of both cyclin E and p27Kip1. The elimination of cyclin E during S and G2 phases is impaired in Skp2−/− cells, resulting in loss of cyclin E periodicity. Biochemical studies showed that Skp2 interacts specifically with cyclin E and thereby promotes its ubiquitylation and degradation both in vivo and in vitro. These results suggest that specific degradation of cyclin E and p27Kip1 is mediated by the SCFSkp2 ubiquitin ligase complex, and that Skp2 may control chromosome replication and centrosome duplication by determining the abundance of cell cycle regulators.

An F-box protein, FWD1, mediates ubiquitin-dependent proteolysis of beta-catenin.

β‐catenin plays an essential role in the Wingless/Wnt signaling cascade and is a component of the cadherin cell adhesion complex. Deregulation of β‐catenin accumulation as a result of mutations in adenomatous polyposis coli (APC) tumor suppressor protein is believed to initiate colorectal neoplasia. β‐catenin levels are regulated by the ubiquitin‐dependent proteolysis system and β‐catenin ubiquitination is preceded by phosphorylation of its N‐terminal region by the glycogen synthase kinase‐3β (GSK‐3β)/Axin kinase complex. Here we show that FWD1 (the mouse homologue of Slimb/βTrCP), an F‐box/WD40‐repeat protein, specifically formed a multi‐molecular complex with β‐catenin, Axin, GSK‐3β and APC. Mutations at the signal‐induced phosphorylation site of β‐catenin inhibited its association with FWD1. FWD1 facilitated ubiquitination and promoted degradation of β‐catenin, resulting in reduced cytoplasmic β‐catenin levels. In contrast, a dominant‐negative mutant form of FWD1 inhibited the ubiquitination process and stabilized β‐catenin. These results suggest that the Skp1/Cullin/F‐box protein FWD1 (SCFFWD1)–ubiquitin ligase complex is involved in β‐catenin ubiquitination and that FWD1 serves as an intracellular receptor for phosphorylated β‐catenin. FWD1 also links the phosphorylation machinery to the ubiquitin–proteasome pathway to ensure prompt and efficient proteolysis of β‐catenin in response to external signals. SCFFWD1 may be critical for tumor development and suppression through regulation of β‐catenin protein stability.

Association between body mass index and mortality in an 80-year-old population.

OBJECTIVES: To evaluate the association between body mass index (BMI) and all‐cause mortality and cardiovascular disease (CVD) in an 80‐year‐old population.

Quality of life and physical fitness in an 85-year-old population

Since little is known about the very elderly population aged 80 years and older, we evaluated the association of quality of life (QoL) in an 85-year-old population with physical fitness measurements assessed at age 80 and 85 years. Two hundred seven individuals (90 males, 117 females) aged 85 years underwent the Short Form-36 (SF-36) questionnaires for QoL assessment and physical fitness measurements (handgrip strength, leg-extensor strength, one-leg standing time, stepping rate of legs, walking speed). In 85-year-olds, significant associations were found, by multiple regression analysis or logistic regression analysis, with adjustment for various influencing factors in QoL assessed by SF-36 with physical fitness measurements examined at the age of 85 and 80 years. Physical scales and scores in SF-36, such as physical functioning (PF), limitation in role functioning for physical reasons (role physical; RP), bodily pain (BP), and the physical component score (PCS) tended to be more tightly associated with fitness measurements than mental scales and scores such as limitation in role functioning for emotional reasons (role emotional; RE), and emotional well-being (mental health; MH), and mental component score (MCS). Three scales the general health perceptions (GH), the vitality (VT), and the social functioning (SF) consisting of both physical and mental components were associated with fitness, the extent being intermediate between physical scales and mental scales. Of the several physical fitness measurements, leg-extensor strength and the walking speed of 85-year-olds, and the stepping rate of 80-year-olds were most closely associated with QoL. In a very elderly population of 85- and 80-year-olds, significant associations were found between QoL by SF-36 and physical fitness measurements, suggesting that increases in the levels of physical fitness, even in the very elderly, can contribute to improvements in QoL.

Physical Fitness and Cognitive Function in an 85-Year-Old Community-Dwelling Population

Background: Little is known about the association between physical fitness and cognitive function in very elderly people (over 80 years of age). Objectives: To evaluate that relationship in 85-year-old community-dwelling individuals. Methods: Out of 207 participants (90 males, 117 females) who were 85 years old and community-dwelling, 205 completed the Mini-Mental State Examination (MMSE) for evaluating cognitive function. The numbers of subjects who completed physical fitness measurements such as hand-grip strength, isometric leg extensor strength, one-leg standing time, stepping rate, and walking speed were 198, 159, 169, 168, and 151, respectively. Results: There were significant associations in MMSE with hand-grip strength (right or left hand), isometric leg extensor strength, stepping rate, and walking speed by simple regression analysis. MMSE was still significantly associated with hand-grip strength (β = 0.305, p = 0.005 for right side; β = 0.309, p = 0.004 for left side), stepping rate (β = 0.183, p = 0.046), and walking speed (β = –0.222, p = 0.014) by multiple regression analysis after adjustments for the amount of education, gender, smoking, drinking, complication of stroke, body weight, body height, regular medical care, serum albumin, blood HbA1c, and marital status. By logistic regression analysis, the prevalence of a normal MMSE score (MMSE ≧24) was increased by 9% with each 1-kg increase in hand-grip strength of the left hand (OR 1.087, 95% CI 1.003–1.179, p = 0.042), and was increased by 6% with each step per 10 s in stepping rate (OR 1.060, 95% CI 1.000–1.122, p = 0.048). Conclusion: In a very elderly population of 85-year-olds, cognitive function was associated with some physical fitness measurements, independent of confounding factors.

Relationship between chewing ability and high‐level functional capacity in an 80‐year‐old population in Japan

OBJECTIVES To evaluate the association between high-level functional capacity and chewing in a middle-old community-based population. BACKGROUND Although basic and instrumental activities of daily living are known to be associated with chewing ability in the elderly, an association between higher levels of competence and chewing ability has not been evaluated in the elderly. MATERIALS AND METHODS The association between chewing ability using a number of different foods and high-level functional capacity by the Tokyo Metropolitan Institute of Gerontology was evaluated in 694, 80-year-old people residing in Fukuoka Prefecture, Japan. RESULTS A significant correlation was found, using multiple regression or logistic regression analyses adjusted for various confounding factors, between the number of total chewable foods, hard foods or moderately hard foods, and total functional capacity, instrumental activity, intellectual activity or social role ability. In contrast, the number of slightly hard foods, easily chewable foods and remaining teeth were only partly related to total functional capacity and intellectual activity. CONCLUSION High-level functional capacity including intellectual activity and social role in middle-old elderly was associated with the ability to chew hard foods than to chew easily chewable foods. Maintenance of chewing ability in elderly might result in better intellectual activity and social role.

Recombinant human granulocyte colony-stimulating factor reduces colonic epithelial cell apoptosis and ameliorates murine dextran sulfate sodium-induced colitis

Objective. Recombinant human granulocyte colony-stimulating factor (rhG-CSF) is a potentially effective therapy for Crohns disease. The purpose of this study was to test the rhG-CSF in murine dextran sulfate sodium-induced colitis (DSS colitis). Material and methods. Murine colitis was induced by feeding with water containing 3% DSS for 9 days. Six to 7-week-old female BALB/c mice were given rhG-CSF (100 µg/kg) or phosphate-buffered saline (PBS) subcutaneously once a day from day 0 to day 8, and the mice were sacrificed at days 3, 5, 7 and 9. Tissue specimens from the transverse colon, descending colon and rectum were obtained and stained with hematoxylin and eosin. Inflammation was scored for severity, extent, epithelial damage and crypt loss. TUNEL staining was performed to assess epithelial cell apoptosis. Results. Treatment with rhG-CSF significantly attenuated body-weight loss, stool score and shortening of the colon length in comparison with treatment with PBS (p<0.01,<0.05,<0.01, respectively). Histological scores for inflammation, epithelial cell damage and crypt loss of the rectum were less severe at day 9 in the rhG-CSF group than in the PBS group (p<0.01, 0.05, 0.01, respectively). The number of TUNEL-positive cells in the rectum was smaller in the rhG-CSF group than in the PBS group (p<0.001). Conclusions. Treatment with rhG-CSF ameliorates murine DSS colitis by suppressing mucosal inflammation and epithelial damage in the rectum. The prevention of epithelial cell apoptosis seems to precede the anti-inflammatory action of rhG-CSF.

Serum microRNA levels in patients with Crohn's disease during induction therapy by infliximab

microRNAs (miRNAs) have been suggested to be candidates for biomarkers in various diseases including Crohns disease (CD). To identify possible biomarkers predictive of the therapeutic effect of infliximab in CD, we investigated serum miRNA levels during the induction therapy by the medication.

Physical fitness and 6.5-year mortality in an 85-year-old community-dwelling population

Although poor physical fitness is known to be associated with increased mortality in adult and elderly populations, this association is not conclusive in very elderly. The purpose of the present study was to evaluate the association for a very old community-dwelling population. The participants (90 males, 117 females) were 85-year-old individuals residing in Fukuoka, Japan. Baseline examinations including muscle strength of the handgrip and leg extension, one-leg standing, leg stepping rate, and walking were performed in 2003 and these subjects were followed for 6.5 years. During the follow-up period, 81 individuals (49 males and 32 females) died. Handgrip strength and leg extension strength at age 85 were stronger in surviving men than in non-survivors. Total mortality adjusted for both gender and serum level of total cholesterol fell 5-6% with a 1-kg increase in the handgrip strength of a single hand or both hands. Total mortality also decreased 2% with a 1 kg increase in the leg extension strength of both legs. With adjustment for gender and total cholesterol, mortality fell by 57% in participants of the walking test and fell by 45% in participants of the stepping-rate test compared to mortality in nonparticipants. No association was found between mortality and participation in the handgrip strength test, leg extension strength test, or one-leg standing time test. In conclusion, not only poor muscle strength in handgrip or leg extension, but also nonparticipation in walking test or leg-stepping test were independent predictors of total mortality in a very elderly population.

Atrophic gastritis, but not antibody to Helicobacter pylori, is associated with body mass index in a Japanese population

BackgroundThe relationship between Helicobacter pylori (HP) infection and body mass index (BMI) is controversial. Several reports have indicated that eradication of HP infection induces an increase in BMI. In contrast, epidemiological case-control studies have failed to show an association between HP infection and BMI. Therefore, we investigated whether HP and atrophic gastritis (AG) were associated with BMI.MethodsA total of 617 individuals were recruited for the measurements of BMI, serum leptin, pepsinogens (PGs) I and II, and IgG antibody to HP (HP-IgG). BMI and leptin of the subjects were compared when the subjects were stratified by HP-IgG and PGs.ResultsThe subjects were divided into AG-positive and AG-negative groups according to PGs (AG-positive: PG I ≤ 70 ng/ml and PG I/II ratio ≤3.0). BMI after adjusting for sex and age was significantly lower in the AG-positive group than in the AG-negative group (23.47 ± 3.05 vs. 24.18 ± 3.25, P = 0.010). When the subjects were divided into two groups according to HP-IgG, BMI tended to be lower in the HP-IgG-positive group, though the difference was not large. When the subjects were divided into four groups for different combinations of AG and HP-IgG, BMI was the lowest in the AG-positive and HP-IgG-negative group.ConclusionsBMI was associated with AG, as diagnosed by PGs, but not with HP infection status. These results mean that HP infection affects BMI via atrophic gastritis.