Japanese lifestyle decreases diabetes prevalence

THE LANCET

SCIENCE AND MEDICINE

Macrophages help nerves regenerate

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mplantation of activated macrophages at the site of nerve injury can encourage neuronal regeneration in the central nervous system (CNS), report Israeli scientists. Although cautious about the clinical application of their findings, the researchers say that it might be possible to develop the procedure as part of a treatment for CNS injuries. When damage occurs in most tissues, macrophages gather at the injured site to clear away any debris. Macrophages also release cytokines and growth factors to promote healing. But immune cells are excluded from the CNS and/or suppressed in the CNS, possibly to avoid inadvertent remodelling of neural connections, so debris arising from CNS injury is not removed. Since myelin debris is known to inhibit axonal growth, Michal Schwartz (Rehovot, Israel) and colleagues reasoned that introduction of appropriately activated macrophages to the injury site might aid CNS regeneration. To test this idea, Schwartz’s team preincubated rat blood monocytes with injured sciatic nerve segments (capable of regeneration) or with optic nerve segments (not capable of regeneration). Only the mono-cytes activated by incubation with sciatic nerves induced biologically significant axonal regrowth when implanted into

injured rat optic nerves (FASEB J 1996; 10: 1296–302). The scientists noted a dose effect in the experiments— implantation of too many activated macrophages caused local neuronal inflammation and degeneration. “Immune assistance is just as vital for the repair of the mammalian CNS as it is for other tissues”, says Schwartz. “By sidestepping a resident suppressive mechanism, we can invoke this assistance.” Controlled application of the patient’s own ex-vivo activated macrophages may prevent or reverse CNS damage, and “combined with treatment modalities designed to increase the number of regrowing axons, to increase neuron survival and to delay nerve degeneration, this could be a potent, novel therapy”, suggests Schwartz. Rachelle H B Fishman

Japanese lifestyle decreases diabetes prevalence

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apanese-American men living in Hawaii who retain a Japanese lifestyle have a decreased risk of non-insulin-dependent diabetes. They are also more physically active and eat a diet with more carbohydrate and less fat and animal protein, according to a recent report. A total of 8006 Japanese-American men, aged between 46 and 65 years at recruitment, were enrolled within the Honolulu Heart Program between 1965 and 1968 . Place of birth, total years lived in Japan, physical activity, diet composition, and self-reported diet type (western, Oriental, or mixed) were recorded. Diabetes was defined as either a self-reported use of diabetic medication, or a history of diabetes plus a non-fasting plasma glucose of greater than 12·5 mmol/L 1 hour after a 50 g oral glucose load. Similar results were found when other definitions of diabetes were used to analyse the data. After adjustment for age, body-mass index, and physical activity there was an inverse association between an Oriental diet and diabetes prevalence (odds ratio 0·71; 95% CI 0·50–0·98). However,

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men with diabetes had an intake of fat that was consistently greater than men without diabetes regardless of diet type (Am J Epidemiol 1996; 144: 674–81). Male Japanese-Americans born in Japan had a significantly lower age-adjusted prevalence of diabetes than those born in Hawaii (5·2% vs 6·4%). This association was independent of age, bodymass index, physical activity, total-calorie intake, or percentage of dietary calories from fat, carbohydrate, or protein. Serum cholesterol or triglycerides were not associated with prevalence of diabetes. The authors suggest that early life factors, which were not recorded in this study, such as birthweight, may be important in diabetes development. K D Hopkins

Vol 348 • October 12, 1996