Metabolic syndrome as a prognostic factor for breast cancer recurrences

CCAAT/enhancer-binding protein beta: its role in breast cancer and associations with receptor tyrosine kinases

The CCAAT/enhancer-binding proteins (C/EBPs) are a family of leucine-zipper transcription factors that regulate gene expression to control cellular proliferation, differentiation, inflammation and metabolism. Encoded by an intronless gene, C/EBPbeta is expressed as several distinct protein isoforms (LAP1, LAP2, LIP) whose expression is regulated by the differential use of several in-frame translation start sites. LAP1 and LAP2 are transcriptional activators and are associated with differentiation, whereas LIP is frequently elevated in proliferative tissue and acts as a dominant-negative inhibitor of transcription. However, emerging evidence suggests that LIP can serve as a transcriptional activator in some cellular contexts, and that LAP1 and LAP2 might also have unique actions. The LIP:LAP ratio is crucial for the maintenance of normal growth and development, and increases in this ratio lead to aggressive forms of breast cancer. This review discusses the regulation of C/EBPbeta activity by post-translational modification, the individual actions of LAP1, LAP2 and LIP, and the functions and downstream targets that are unique to each isoform. The role of the C/EBPbeta isoforms in breast cancer is discussed and emphasis is placed on their interactions with receptor tyrosine kinases.

Sex hormone levels, breast cancer risk, and cancer receptor status in postmenopausal women: the ORDET cohort

BACKGROUND

Endogenous sex hormone levels have been associated with increased breast cancer risk in postmenopausal women in several prospective studies. However, it remains unclear to what extent serum hormone-breast cancer associations differ with receptor status.

METHODS

Associations between serum sex hormone levels and breast cancer risk were assessed in a nested case-control study on postmenopausal women of the ORDET cohort. After a median follow-up of 13.5 years, 165 women developed breast cancer. Relative risks of developing breast cancer were estimated by conditional logistic regression.

RESULTS

Total and free testosterone levels were directly associated with breast cancer risk [relative risk, 3.28 (95% confidence interval, 1.93-5.55) and 2.86 (95% confidence interval, 1.66-4.94), respectively, for highest versus lowest quartile]. When relations between hormone level and risk of breast cancer expressing various receptor combinations were assessed, high total testosterone was significantly associated with increased risk of estrogen receptor-positive cancers, irrespective of progesterone receptor status. High total testosterone was also associated with increased risk of both human epidermal growth factor receptor 2 (HER2)-negative (HER2(-)) and HER2(+) cancers. High estradiol tended to be associated with increased risk of HER2(-) cancer and inversely associated with HER2(+) cancer, with significant (P = 0.027) heterogeneity between HER2(+) and HER2(-) cancers. However, there were relatively few HER2(+) cases.

CONCLUSIONS

This study provides further evidence that high levels of circulating testosterone increase the risk of developing breast cancer in postmenopausal women. The cancers that develop are mainly estrogen receptor positive. Although HER2(+) and HER2(-) breast cancers were both associated with high total testosterone, they showed opposing associations with estrogen.

Insulin-lowering effects of metformin in women with early breast cancer

BACKGROUND

Obesity has been associated with poor breast cancer outcomes. Insulin may mediate this effect, interacting with insulin receptors on breast cancer cells. Metformin, a biguanide derivative used in the treatment of diabetes, reduces insulin levels in subjects with type 2 diabetes and other insulin-resistant states. If metformin lowers insulin levels in women with breast cancer, it may also improve breast cancer outcomes.

PATIENTS AND METHODS

We administered metformin (1500 mg per day) to 32 women with early breast cancer whose baseline insulin levels were at least 45 pmol/L to determine its effect on insulin levels.

RESULTS

Twenty-two (69%) women completed the 6-month intervention. Four women (12.5%) dropped out because of gastrointestinal side effects; the others withdrew for reasons not related to toxicity. Completers were similar to noncompleters for all baseline characteristics apart from global health, overall physical condition, overall quality of life, physical function, and social function (HRQOL), which was decreased in noncompleters. Metformin significantly lowered fasting insulin levels by 15.8 pmol/L (22.4%; P=.024) and improved insulin sensitivity by 25.6% (P=.018), total cholesterol by 5.3%, and low-density lipoprotein (LDL) cholesterol by 9.1%. Metformin reduced weight by 1.9 kg (2.5%; P=.01), and it had no significant effects on HRQOL or specific gastrointestinal symptoms (appetite, nausea/vomiting, diarrhea, constipation).

CONCLUSION

Metformin significantly lowers insulin levels, and it improves insulin resistance in nondiabetic women with breast cancer. A phase III randomized trial to evaluate its effects on breast cancer outcomes is recommended.

Physical activity and breast cancer survival

Physical activity improves quality of life after a breast cancer diagnosis, and a beneficial effect on survival would be particularly welcome. Four observational studies have now reported decreased total mortality among physically active women with breast cancer; the two largest have also reported decreased breast cancer specific mortality. The estrogen pathway and the insulin pathway are two potential mechanisms by which physical activity could affect breast cancer survival. Randomized trials are ongoing but trials of lifestyle factors are notoriously challenging to perform. Women with breast cancer have little to lose and may possibly gain from moderate exercise.

Effect of fenretinide and low-dose tamoxifen on insulin sensitivity in premenopausal women at high risk for breast cancer

The prevalence of metabolic syndrome is increasing along with breast cancer incidence worldwide. Because fenretinide improves insulin action and glucose tolerance in insulin-resistant obese mice and because tamoxifen has shown to regulate several markers involved in metabolic syndrome, we sought to investigate the effect of fenretinide or tamoxifen at low dose on features linked to insulin resistance in premenopausal women at risk for breast cancer. We randomized 235 women to low-dose tamoxifen (5 mg/daily), fenretinide (200 mg/daily), or their combination or placebo for 2 years. We used the homeostasis model assessment (HOMA; fasting insulin x glucose/22.5) to estimate insulin sensitivity. Women were considered to improve insulin sensitivity when they shifted from a HOMA >/=2.8 to <2.8. There was no effect of fenretinide or tamoxifen on HOMA overall, but overweight women (body mass index, >or=25 kg/m(2)) had a 7-fold greater probability to normalize HOMA after 2 years of fenretinide treatment [odds ratio (OR), 7.0; 95% confidence interval (95% CI), 1.2-40.5], with 25% of women improving their insulin sensitivity, whereas tamoxifen decreased insulin sensitivity by almost 7 times compared with subjects not taking tamoxifen (OR, 0.15; 95% CI, 0.03-0.88). In this group only, 5% improved their insulin sensitivity. Interestingly, women with intraepithelial or microinvasive neoplasia had higher HOMA (3.0) than unaffected subjects (2.8; P = 0.07). Fenretinide can positively balance the metabolic profile in overweight premenopausal women and this may favorably affect breast cancer risk. Furthermore, features of the metabolic syndrome should be taken into consideration before proposing tamoxifen for breast cancer prevention. The clinical implications of these results require further investigations.

Insulin, the insulin-like growth factor axis, and mortality in patients with nonmetastatic colorectal cancer

PURPOSE

Obesity, sedentary lifestyle, and Western dietary pattern have been linked to increased risk of cancer recurrence and mortality among patients with surgically resected colorectal cancer. Excess energy balance leads to increased circulating insulin and depressed levels of circulating insulin-like growth factor binding protein (IGFBP) -1, which promote cancer cell growth in preclinical models.

PATIENTS AND METHODS

Among 373 patients diagnosed with nonmetastatic colorectal cancer between 1991 and 2004, we performed a prospective observational study nested within two large US cohorts to evaluate the association between mortality and prediagnosis circulating C-peptide (a marker of insulin secretion), IGFBP-1, insulin-like growth factor-I (IGF-I), and IGFBP-3.

RESULTS

Compared with patients in the bottom quartile, patients in the top quartile of plasma C-peptide had an age-adjusted hazard ratio (HR) for death of 1.87 (95% CI, 1.04 to 3.36; P = .03 for trend), whereas those in the top quartile of circulating IGFBP-1 had a significant reduction in mortality (HR = 0.48; 95% CI, 0.28 to 0.84; P = .02 for trend). Little change in these estimates was noted after adjusting for other covariates known or suspected to influence survival. No associations were noted between mortality and IGF-I or IGFBP-3, which are two components of the IGF axis not closely correlated with lifestyle factors.

CONCLUSION

Among patients with surgically resected colorectal cancer, higher levels of prediagnosis plasma C-peptide and lower levels of prediagnosis plasma IGFBP-1 were associated with increased mortality. Circulating insulin and IGFBP-1 are potential mediators of the association between lifestyle factors and mortality after colorectal cancer resection.

Serum insulin-like growth factor-I and platelet-derived growth factor as biomarkers of breast cancer prognosis

Epidemiologic studies have shown that growth factors and inflammatory mechanisms may affect breast cancer risk and prognosis. The present analysis on 110 postmenopausal breast cancer patients tested if serum insulin-like growth factor I (IGF-I), platelet-derived growth factor (PDGF), fructosamine, and C-reactive protein, a serum marker of inflammation, are associated with breast cancer relapse. The risk of adverse events after 5.5 years of follow-up was examined by Cox proportional hazards modeling, controlling for hormone receptor status, stage at diagnosis, and for body weight and serum testosterone level, which were known to significantly affect prognosis. PDGF and, to a lesser extent, IGF-I were positively but not significantly associated with the risk of breast cancer recurrence. By combining PDGF and IGF-I, however, the adjusted hazard ratio of recurrence among the women with both PDGF and IGF-I levels > their median values (respectively, 9.3 and 174.4 ng/mL) was 6.4 (95% confidence interval, 1.5-26.7) compared with the women with PDGF and IGF-I levels < or = their median values. Fructosamine and C-reactive protein were not associated with recurrences. The results suggest that PDGF may be an important prognostic factor for breast cancer and that IGF-I may increase the risk of recurrence in the presence of high PDGF levels.

Insulin-dependent leptin expression in breast cancer cells

Pathologic conditions associated with hyperinsulinemia, such as obesity, metabolic syndrome, and diabetes, seem to increase the risk of breast cancer. Here, we studied molecular mechanisms by which insulin activates the expression of leptin, an obesity hormone that has been shown to promote breast cancer progression in an autocrine or paracrine way. Using MDA-MB-231 breast cancer cells, we found that (a) insulin stimulated leptin mRNA and protein expression, which was associated with increased activation of the leptin gene promoter; (b) insulin increased nuclear accumulation of transcription factors hypoxia inducible factor (HIF)-1alpha and Sp1 and their loading on the leptin promoter; (c) small interfering RNA (siRNA)-mediated knockdown of either HIF-1alpha or Sp1 significantly down-regulated insulin-induced leptin mRNA and protein expression; further inhibition of leptin expression was observed under the combined HIF-1alpha and Sp1 siRNA treatment; (d) inhibition of extracellular signal-regulated kinase (ERK)1/2 and phosphatidylinositol-3-OH kinase (PI-3K) pathways significantly, albeit partially, decreased insulin-dependent leptin mRNA and protein expression, which coincided with reduced association of HIF-1alpha and/or Sp1 with specific leptin promoter regions; and (e) inhibition of ERK1/2 reduced recruitment of both HIF-1alpha and Sp1 to the leptin promoter, whereas down-regulation of PI-3K influenced only HIF-1alpha binding. In summary, our data suggest that hyperinsulinemia could induce breast cancer progression through leptin-dependent mechanisms. In MDA-MB-231 cells, this process requires Sp1- and HIF-1alpha-mediated leptin gene transcription and is partially regulated by the PI-3K and ERK1/2 pathways.

High insulin levels in newly diagnosed breast cancer patients reflect underlying insulin resistance and are associated with components of the insulin resistance syndrome

BACKGROUND

High insulin levels have been associated with poor outcomes in breast cancer. Our goal was to investigate whether hyperinsulinemia was associated with insulin resistance in a cohort of newly diagnosed locoregional breast cancer patients and to examine associations of hyperinsulinemia with the broader insulin resistance syndrome (IRS).

METHODS

Five hundred and four women with T1-3, N0-1, M0 breast cancer provided fasting blood that was analyzed for glucose, insulin and lipids. They underwent anthropomorphic measurements and provided information on diet, exercise and sleep. Relationships of insulin with three validated indices of insulin resistance and with attributes of the IRS were examined.

RESULTS

High insulin levels were strongly correlated with insulin resistance calculated using the three indices of insulin resistance/sensitivity (Spearman r=0.83-0.98). Hyperinsulinemia was also associated with other components of the IRS (obesity, high waist-hip ratio, lipid profile).

CONCLUSIONS

High insulin levels in women with locoregional breast cancer reflect the presence of insulin resistance and are associated with other components of the IRS. These observations have implications for the development of therapies that target hyperinsulinemia in early stage breast cancer and for the long-term management of breast cancer survivors.

Impact of a mixed strength and endurance exercise intervention on insulin levels in breast cancer survivors

PURPOSE

Accumulating data suggest that exercise may affect breast cancer risk and outcomes. Studies have demonstrated that high levels of insulin, often seen in sedentary individuals, are associated with increased risk of breast cancer recurrence and death. We sought to analyze whether exercise lowered insulin concentrations in breast cancer survivors.

METHODS

One hundred one sedentary, overweight breast cancer survivors were randomly assigned either to a 16-week cardiovascular and strength training exercise intervention or to a usual care control group. Fasting insulin and glucose levels, weight, body composition, and circumference at the waist and hip were collected at baseline and 16 weeks.

RESULTS

Baseline and 16-week measurements were available for 82 patients. Fasting insulin concentrations decreased by an average of 2.86 microU/mL in the exercise group (P = .03), with no significant change in the control group (decrease of 0.27 microU/mL, P = .65). The change in insulin levels in the exercise group seemed greater than the change in controls, but the comparison did not reach statistical significance (P = .07). There was a trend toward improvement in insulin resistance in the exercise group (P = .09) but no change in fasting glucose levels. The exercise group also experienced a significant decrease in hip measurements, with no change in weight or body composition.

CONCLUSION

Participation in an exercise intervention was associated with a significant decrease in insulin levels and hip circumference in breast cancer survivors. The relationship between physical activity and breast cancer prognosis may be mediated, in part, through changes in insulin levels and/or changes in body fat or fat deposition.

Adiposity, the metabolic syndrome, and breast cancer in African-American and white American women

Breast cancer, the second most common cause of cancer-related deaths in American women, varies substantially in incidence and mortality according to race and ethnicity in the United States. Although the overall incidence of breast cancer among African-American (AA) women is lower than in white American women, this cancer is more common in young premenopausal AA women, and AA breast cancer patients of all ages are more likely to have advanced disease at diagnosis, higher risk of recurrence, and poorer overall prognosis. Epidemiological studies indicate that these differences may be attributable in part to variation in obesity and body fat distribution. Additionally, AA women more frequently exhibit breast cancer with an aggressive and metastatic phenotype that may also be attributable to the endocrine and metabolic changes associated with upper body obesity. These changes include both elevated estrogen and androgen bioactivity, hyperinsulinemia, and perturbations of the adipokines. Type 2 diabetes and the metabolic syndrome, which are more common in AA women, have also been associated with breast cancer risk. Moreover, each of the individual components of the syndrome has been associated with increased breast cancer risk, including low levels of the adipocytokine, adiponectin. This review explores the specific roles of obesity, body fat distribution (particularly visceral and sc adipose tissue), type 2 diabetes, metabolic syndrome, and adipocytokines in explaining the differential patterns of breast cancer risk and prognosis between AA and white American women.

Symposium introduction: metabolic syndrome and the onset of cancer

Diabetes, obesity, and related metabolic disorders are among the most pressing of today's health care concerns. Recent evidence from epidemiologic and basic research studies, as well as translational, clinical, and intervention studies, supports the emerging hypothesis that metabolic syndrome may be an important etiologic factor for the onset of cancer. On March 15-16, 2006, The Harvard Medical School Division of Nutrition hosted the symposium "Metabolic Syndrome and the Onset of Cancer" as a platform to systematically evaluate the evidence in support of this hypothesis. This symposium, which gathered leaders in the fields of metabolism, nutrition, and cancer, will stimulate further research investigating the etiologic role of metabolic syndrome in cancer. Furthermore, it will help to guide the development of effective cancer prevention strategies via nutritional and lifestyle modifications to alleviate metabolic syndrome.

Adiposity, type 2 diabetes and the metabolic syndrome in breast cancer

Upper body obesity and the related metabolic disorder type 2 diabetes have been identified as risk factors for breast cancer, and associated with late-stage disease and a poor prognosis. Components of the metabolic syndrome, including visceral adiposity, insulin resistance, hyperglycemia and hyperinsulinemia, with or without clinically manifest diabetes mellitus, low serum high-density lipoprotein cholesterol and hypertension have all been related to increased breast cancer risk. The biochemical mechanisms include extraglandular oestrogen production, reduced sex hormone-binding globulin with consequent elevation of the bioactive plasma free oestradiol and increased insulin biosynthesis, all of which exert mitogenic effects on both untransformed and neoplastic breast epithelial cells. Obesity, type 2 diabetes and the metabolic syndrome also have in common an increased production of leptin and a decreased production of adiponectin by adipose tissue, with consequent elevations and reductions, respectively, in the circulating levels of these two adipokines. These changes in plasma leptin and adiponectin, acting through endocrine and paracrine mechanisms, have been associated in several studies with an increase in breast cancer risk and, perhaps, to more aggressive tumours; studies in vitro showed that leptin stimulates, and adiponectin inhibits, tumour cell proliferation and the microvessel angiogenesis which is essential for breast cancer development and progression.

Dietary soy and tea combinations for prevention of breast and prostate cancers by targeting metabolic syndrome elements in mice

BACKGROUND

The prevalence of metabolic syndrome is high and is increasing in parallel with increasing incidences of breast and prostate cancers. The combination of soy with tea was shown to have synergistic effects on preventing breast and prostate tumors, but the effects of soy and tea combinations on metabolic syndrome-related elements have not been investigated.

OBJECTIVE

We aimed to determine the effects of soy and tea components, alone and in combination, on abdominal adipose mass and serum concentrations of adipokines, growth factors, and sex hormones in male and female mice.

DESIGN

Male and female FVB/N mice were treated with soy, tea components, or both. Food intake and body weight were monitored weekly. At the end of the experiment, abdominal white adipose tissue was weighed, and serum concentrations of biomarkers were measured.

RESULTS

Whole teas, but not the tea polyphenol extracts, significantly reduced abdominal white adipose tissue by 43-60% in female mice and by 65-70% in male mice. The combination of soy phytochemical concentrate and green tea reduced serum insulin-like growth factor-I concentrations in both male and female mice in a synergistic manner. The soy phytochemical concentrate and tea combinations reduced serum estrogen concentrations in female mice in a synergistic manner. Soy phytochemical concentrate and teas also significantly reduced serum leptin concentrations in both male and female mice and testosterone concentrations in male mice.

CONCLUSION

Further research is warranted to investigate whether soy and tea combinations may prevent breast or prostate cancer in a synergistic manner in part by alleviating metabolic disorders.

The impact of diabetes on survival following breast cancer

PURPOSE

It has been suggested that type 2 diabetes may affect breast cancer prognosis, possibly due to increased diabetes-related comorbidity, or direct effects of insulin resistance and/or hyperinsulinemia. The purpose of this study was to examine the impact of diabetes on survival following breast cancer.

METHODS

Using population-based health databases from Ontario, Canada, this retrospective cohort study compared deaths between women with breast cancer aged 55-79 years with diabetes and without diabetes. Women were followed for all cause mortality from breast cancer diagnosis until March 31st 2006.

RESULTS

Of the 6,107 women with breast cancer, 1,011 had diabetes and 5,096 did not have diabetes. Women with diabetes were slightly older, were more likely to reside in a lower income neighborhood, and had greater comorbidity compared to women without diabetes. After a mean follow-up of 5.0 years and adjustment for age, prior mammograms and other covariates, mortality following breast cancer was significantly higher among women with versus without diabetes (hazard ratio, HR 1.39, 95% confidence interval, CI 1.22-1.59, P < 0.0001). The effect of diabetes on mortality was comparable to that seen in women with diabetes without breast cancer over a 7-year follow-up.

CONCLUSION

This study found that diabetes was associated with a close to 40% increase in mortality within the first 5 years following breast cancer, which was similar to that seen in women with diabetes without breast cancer. These findings suggest that early survival following breast cancer is reduced in women with diabetes, possibly due to diabetes-related causes.

Plasma Testosterone and Prognosis of Postmenopausal Breast Cancer Patients

Purpose

High endogenous testosterone is associated with increased breast cancer (BC) risk. We designed this study specifically to assess the long-term prognostic role of testosterone in a cohort of postmenopausal BC patients.

Patients and Methods

We considered 194 postmenopausal women, operated on for early BC (T1-2N0M0), who never received chemotherapy or hormonal therapy, and who participated in a fenretinide BC prevention trial as untreated controls. Blood samples were collected 3 months (median) after surgery; plasma samples, stored at −80°C, were radioimmunoassayed for testosterone. Median follow-up was 14 years. The main end point was any cancer event. Event-free survival was estimated by the Kaplan-Meier method. Hazard ratios (HRs) of events by testosterone level were estimated by the Cox model, adjusting for age, tumor size, and histology.

Results

Patients with high testosterone (≥ 0.40 ng/mL, median of distribution) had significantly lower event-free survival than those with low testosterone (log-rank P = .004). The adjusted HR of patients with high versus low testosterone was 2.05 (95% CI, 1.28 to 3.27). High testosterone was also associated with a significantly higher risk of BC events (relapse and second primary) with an adjusted HR of 1.77 (95% CI, 1.06 to 2.96). Eleven second primaries (non-BC) occurred in the high-testosterone group, four in the low-testosterone group.

Conclusion

High plasma testosterone strongly predicts poorer prognosis in postmenopausal BC patients not administered adjuvant therapy. Testosterone levels should be determined as part of the prognostic work-up.

Insulin receptor is an independent predictor of a favorable outcome in early stage breast cancer

Fasting insulin is related to outcome in early breast cancer. We evaluated the expression of insulin receptor (IR) and its prognostic significance in patients with early stage breast cancer. Tumors from 191 patients with T1-3, N0-1, M0 breast cancer who were enrolled at a single center of a multicenter cohort study were used to construct microarrays with subsequent immunohistochemical evaluation of IR, IGF-IR, ER, PgR and HER2/neu. Correlation of biomarker expression with traditional prognostic factors, serum biochemistry (notably insulin) and clinical outcome was assessed. IR was strongly positive (Allred score = 8) in 54% of tumors. High IR expression significantly correlated with favorable prognostic markers (low tumor grade, lymph node negativity and progesterone receptor positivity) but not with fasting levels of circulating insulin. At a median follow-up of 9.1 years, high vs. low IR expression (an Allred score of 8 vs. 0-7) was associated with statistically significant improved distant disease-free survival (multivariate hazard ratio (HR) = 0.4; P = 0.027) and overall survival (multivariate HR = 0.26; P = 0.005). IR is highly expressed in the majority of early stage breast cancers but this expression is not clearly down-regulated in the presence of high insulin levels. Furthermore, high expression of IR is independently and significantly associated with more favorable clinical outcomes. Follow-up intervention research is recommended.

The metabolic syndrome: A high-risk state for cancer?

The metabolic syndrome is composed of cardiovascular risk factors including increased body mass index/waist circumference, blood pressure, plasma glucose, and triglycerides, as well as decreased high-density lipoprotein cholesterol. The essence of the metabolic syndrome lies in the clustering of these risk factors, which are associated with cardiovascular disease. Interestingly, most of the components of the metabolic syndrome have individually been linked in some way to the development of cancer. However, epidemiological studies linking the metabolic syndrome to cancer are scarce. Nevertheless, two such studies indicate that the clustering of metabolic syndrome components significantly increases the risk of colon cancer mortality compared with the individual components. The purpose of this review is to further explore the potential relationship between the metabolic syndrome and cancer risk. Specifically, we examine the hypothesis that individual components of the metabolic syndrome contribute to the development of several processes, including insulin resistance, aromatase activity, adipokine production, angiogenesis, glucose utilization, and oxidative stress/DNA damage, which can work together to increase cancer risk beyond that of the individual components alone. We propose that the metabolic syndrome be considered as a high-risk state for certain types of cancer and that this relationship should be systematically explored across cancer types.

Adjuvant Diet to Improve Hormonal and Metabolic Factors Affecting Breast Cancer Prognosis

Western lifestyle, characterized by reduced physical activity and a diet rich in fat, refined carbohydrates, and animal protein is associated with high prevalence of overweight, metabolic syndrome, insulin resistance, and high plasma levels of several growth factors and sex hormones. Most of these factors are associated with breast cancer risk and, in breast cancer patients, with increased risk of recurrences. Recent trials have proven that such a metabolic and endocrine imbalance can be favorably modified through comprehensive dietary modification, shifting from Western to Mediterranean and macrobiotic diet.