Dietary methionine restriction increases fat oxidation in obese adults with metabolic syndrome.

OBJECTIVE: In preclinical reports, restriction of dietary methionine intake was shown to enhance metabolic flexibility, improve lipid profiles, and reduce fat deposition. The present report is the outcome of a "proof of concept" study to evaluate the efficacy of dietary methionine restriction (MR) in humans with metabolic syndrome. METHODS: Twenty-six obese subjects (six male and 20 female) meeting criteria for metabolic syndrome were randomized to a diet restricted to 2 mg methionine/kg body weight per day and were provided capsules containing either placebo (n = 12) or 33 mg methionine/kg body weight per day (n = 14). Energy expenditure, body composition, insulin sensitivity, and biomarkers of metabolic syndrome were measured before and after 16 wk on the respective diets. RESULTS: Insulin sensitivity and biomarkers of metabolic syndrome improved comparably in both dietary groups. Rates of energy expenditure were unaffected by the diets, but dietary MR produced a significant increase in fat oxidation (MR, 12.1 ± 6.0% increase; control, 8.1 ± 3.3% decrease) and reduction in intrahepatic lipid content (MR liver/spleen attenuation ratio, 8.1 ± 3.3% increase; control ratio, 2.2 ± 2.1% increase) that was independent of the comparable reduction in weight and adiposity that occurred in both groups. CONCLUSIONS: Sixteen weeks of dietary MR in subjects with metabolic syndrome produced a shift in fuel oxidation that was independent of the weight loss, decreased adiposity, and improved insulin sensitivity that was common to both diets.

Dietary methionine restriction enhances metabolic flexibility and increases uncoupled respiration in both fed and fasted states.

Dietary methionine restriction (MR) is a mimetic of chronic dietary restriction (DR) in the sense that MR increases rodent longevity, but without food restriction. We report here that MR also persistently increases total energy expenditure (EE) and limits fat deposition despite increasing weight-specific food consumption. In Fischer 344 (F344) rats consuming control or MR diets for 3, 9, and 20 mo, mean EE was 1.5-fold higher in MR vs. control rats, primarily due to higher EE during the night at all ages. The day-to-night transition produced a twofold higher heat increment of feeding (3.0 degrees C vs. 1.5 degrees C) in MR vs. controls and an exaggerated increase in respiratory quotient (RQ) to values greater than 1, indicative of the interconversion of glucose to lipid by de novo lipogenesis. The simultaneous inhibition of glucose utilization and shift to fat oxidation during the day was also more complete in MR (RQ approximately 0.75) vs. controls (RQ approximately 0.85). Dietary MR produced a rapid and persistent increase in uncoupling protein 1 expression in brown (BAT) and white adipose tissue (WAT) in conjunction with decreased leptin and increased adiponectin levels in serum, suggesting that remodeling of the metabolic and endocrine function of adipose tissue may have an important role in the overall increase in EE. We conclude that the hyperphagic response to dietary MR is matched to a coordinated increase in uncoupled respiration, suggesting the engagement of a nutrient-sensing mechanism, which compensates for limited methionine through integrated effects on energy homeostasis.

Methionine restriction effects on 11 -HSD1 activity and lipogenic/lipolytic balance in F344 rat adipose tissue.

Methionine restriction (MR) limits age-related adiposity in Fischer 344 (F344) rats. To assess the mechanism of adiposity resistance, the effect of MR on adipose tissue (AT) 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) was examined. MR induced 11beta-HSD1 activity in all ATs, correlating with increased tissue corticosterone. However, an inverse relationship between 11beta-HSD1 activity and adipocyte size was observed. Because dietary restriction controls lipogenic and lipolytic rates, MR's effects on lipogenic and lipolytic enzymes were evaluated. MR increased adipose triglyceride lipase and acetyl-coenzyme A carboxylase (ACC) protein levels but induced ACC phosphorylation at serine residues that render the enzyme inactive, suggesting alterations of basal lipolysis and lipogenesis. In contrast, no changes in basal or phosphorylated hormone-sensitive lipase levels were observed. ACC-phosphorylated sites were specific for AMP-activated protein kinase (AMPK); therefore, AMPK activation was evaluated. Significant differences in AMPKalpha protein, phosphorylation, and activity levels were observed only in retroperitoneal fat from MR rats. No differences in protein kinase A phosphorylation and intracellular cAMP levels were detected. In vitro studies revealed increased lipid degradation and a trend toward increased lipid synthesis, suggesting the presence of a futile cycle. In conclusion, MR disrupts the lipogenic/lipolytic balance, contributing importantly to adiposity resistance in F344 rats.

Transcriptional response to aging and caloric restriction in heart and adipose tissue.

Sustained caloric restriction (CR) extends lifespan in animal models but the mechanism and primary tissue target(s) have not been identified. Gene expression changes with aging and CR were examined in both heart and white adipose tissue (WAT) of Fischer 344 (F344) male rats using Affymetrix RAE 230 arrays and validated by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on 18 genes. As expected, age had a substantial effect on transcription on both tissues, although only 21% of cardiac age-associated genes were also altered in WAT. Gene set enrichment analysis revealed coordinated small magnitude changes in ribosomal, proteasomal, and mitochondrial genes with similarities in aging between heart and WAT. CR had very different effects on these two tissues at the transcriptional level. In heart, very few age-associated expression changes were affected by CR, while in WAT, CR suppressed a substantial subset of the age-associated changes. Genes unaltered by aging but altered by CR were identified in WAT but not heart. Most interestingly, we identified a gene expression signature associated with mammalian target of rapamycin (mTOR) activity that was down-regulated with age but preserved by CR in both WAT and heart. In addition, lipid metabolism genes, particularly those associated with peroxisome proliferator-activated receptor gamma (PPARgamma)-mediated adipogenesis were reduced with age but preserved with CR in WAT. These results highlight tissue-specific differences in the gene expression response to CR and support a role for CR-mediated preservation of mTOR activity and adipogenesis in aging WAT.

Methionine restriction decreases visceral fat mass and preserves insulin action in aging male Fischer 344 rats independent of energy restriction.

Reduced dietary methionine intake (0.17% methionine, MR) and calorie restriction (CR) prolong lifespan in male Fischer 344 rats. Although the mechanisms are unclear, both regimens feature lower body weight and reductions in adiposity. Reduced fat deposition in CR is linked to preservation of insulin responsiveness in older animals. These studies examine the relationship between insulin responsiveness and visceral fat in MR and test whether, despite lower food intake observed in MR animals, decreased visceral fat accretion and preservation of insulin sensitivity is not secondary to CR. Accordingly, rats pair fed (pf) control diet (0.86% methinone, CF) to match the food intake of MR for 80 weeks exhibit insulin, glucose, and leptin levels similar to control-fed animals and comparable amounts of visceral fat. Conversely, MR rats show significantly reduced visceral fat compared to CF and PF with concomitant decreases in basal insulin, glucose, and leptin, and increased adiponectin and triiodothyronine. Daily energy expenditure in MR animals significantly exceeds that of both PF and CF. In a separate cohort, insulin responses of older MR animals as measured by oral glucose challenge are similar to young animals. Longitudinal assessments of MR and CF through 112 weeks of age reveal that MR prevents age-associated increases in serum lipids. By 16 weeks, MR animals show a 40% reduction in insulin-like growth factor-1 (IGF-1) that is sustained throughout life; CF IGF-1 levels decline much later, beginning at 112 weeks. Collectively, the results indicate that MR reduces visceral fat and preserves insulin activity in aging rats independent of energy restriction.

Transplants from balding and hairy androgenetic alopecia scalp regrow hair comparably well on immunodeficient mice.

Human hair follicles were grafted onto 2 strains of immunodeficient mice to compare the regeneration potential of vellus (miniaturized, balding) and terminal (hairy, nonbalding) follicles from males and a female exhibiting pattern baldness. Each mouse had transplants of both types of follicles from a single donor for direct comparison. Grafted follicles from 2 male donors resulted in nonsignificant differences in mean length (52 mm vs 54 mm) and mean diameter (99 microm vs 93 microm) at 22 weeks for hairs originating from balding and hairy scalp, respectively, corresponding to 400% versus 62% of the mean pretransplantation diameters. Follicles from the female donor transplanted to several mice also resulted in nonsignificant differences in length (43 mm vs 37 mm) for hairs from balding and hairy scalp, respectively, during a period of 22 weeks. The mean diameter of the originally vellus hairs increased 3-fold, whereas the terminal hairs plateaued at approximately 50% of pretransplantation diameter, resulting in a final balding hair volume double that of the nonbalding hairs. This report shows that miniaturized hair follicles of pattern alopecia can quickly regenerate once removed from the human scalp and can grow as well as or better than terminal follicles from the same individual.

Insulin-like growth factor I (IGF-I), IGF-binding proteins, and breast cancer.

Epidemiological evidence supports a role for the insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) in the induction and progression of various cancers. Estrogen, which plays a role in the etiology of breast cancer, both regulates and is influenced by the IGF family. Risk of breast cancer associated with serum levels of IGF-I and/or IGFBPs may therefore depend upon menopausal status. A nested, case-control study was conducted on 66 women who were premenopausal and 60 who were postmenopausal at the time of diagnosis of primary breast cancer; they were selected from a cohort of 95,000 women who underwent multiphasic health check-ups > 30 years ago when enrolled in the Kaiser Permanente Medical Care Program. For each case, one control who matched by age, date of examination, and length of follow-up was chosen. Concentrations of IGF-I, insulin, glucose, and IGFBP-1, IGFBP-2, and IGFBP-3 in serum drawn at least 2 years before diagnosis (mean times of 10.5 and 15.8 years for pre- and postmenopausal cases, respectively) were compared using conditional logistic regression analysis. All statistical tests were two-sided. Serum IGF-I, adjusted for insulin, glucose, and body mass index, was weakly associated with breast cancer risk across quartiles for premenopausal women only (P for trend = 0.05). Serum IGFBP-3 was higher in premenopausal cases versus controls (P = 0.04) and showed a positive trend in risk for increasing quartiles (P for trend = 0.033). After adjusting for insulin, glucose, body mass index, and IGF-I, premenopausal women in the highest quartile of IGFBP-3 had an elevated risk of breast cancer [odds ratio (OR) = 5.28, 95% confidence interval (CI) = 1.13-24.7]. Conversely, IGFBP-3 was lower in postmenopausal cases versus controls (P = 0.04) but showed no significant trend in risk. Postmenopausal women with glucose levels in the diabetic range were at increased risk for developing breast cancer (OR = 2.06, 95% CI = 0.87-4.91), whereas those in the highest quartile of IGFBP-2 had a substantial reduction (71%) in risk relative to those in the lowest quartile (OR = 0.29, 95% CI = 0.09-0.92). Serum IGFBP-1 was not associated with breast cancer risk in either pre- or postmenopausal women. In premenopausal women, elevated serum IGF-I and IGFBP-3 are associated with increased breast cancer risk, whereas elevated serum IGFBP-2 is inversely associated with risk of postmenopausal breast cancer.