William F. Horn

Conjugated linoleic acid supplementation in humans: effects on circulating leptin concentrations and appetite.

Conjugated linoleic acid (CLA) has been demonstrated to reduce body fat in animals. However, the mechanism by which this reduction occurs is unknown. Leptin may mediate the effect of CLA to decrease body fat. We assessed the effects of 64 d of CLA supplementation (3 g/d) on circulating leptin, insulin, glucose, and lactate concentrations in healthy women. Appetite was assessed as a physiological correlate of changes in circulating leptin levels. Analysis of plasma leptin concentrations adjusted for adiposity by using fat mass as a covariate showed that CLA supplementation significantly decreased circulating leptin concentrations in the absence of any changes of fat mass. Mean leptin levels decreased over the first 7 wk and then returned to baseline levels over the last 2 wk of the study in the CLA-treated group. Appetite parameters measured at around the time when the greatest decreases in leptin levels were observed showed no significant differences between supplementation and baseline determinations in the CLA-supplemented group or between the CLA and placebo-supplemented groups. There was a nonsignificant trend for mean insulin levels to increase toward the end of the supplementation period in CLA-treated subjects. CLA did not affect plasma glucose and lactate over the treatment period. Thus, 64 d of CLA supplementation in women produced a transient decrease in leptin levels but did not alter appetite. CLA did not affect these parameters in a manner that promoted decreases of adiposity.

Conjugated linoleic acid supplementation in humans: Effects on fatty acid and glycerol kinetics

Recent studies with mouse adipocytes have shown that dietary conjugated linoleic acid (CLA) may reduce body fat by increasing lipolysis. The present study examined the effect of CLA supplementation on fatty acid and glycerol kinetics in six healthy, adult women who were participating in a controlled metabolic ward study. These women were fed six CLA capsules per day (3.9 g/d) for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94-d study, where diet and activity were controlled and held constant. The rate of appearance (Ra) of glycerol, which indicates lipolytic rates, was similar at baseline and after 4 wk of CLA supplementation at rest (1.87±0.21 and 2.00±0.39 μmol/kg/min, respectively) and during exercise (7.12±0.74 and 6.40±0.99 μmol/kg/min, respectively). Likewise, the Ra of free fatty acids (FFA) was not significantly different after 4 wk of dietary CLA at rest (2.72±0.06 and 2.74±0.12 μmol/kg/min, respectively) or during exercise (6.99±0.40 and 5.88±0.29 μmol/kg/min, respectively). CLA supplementation also had no effect on the percentage of FFA released from lipolysis that were re-esterified. The apparent rate of FFA re-esterification was 65.2±4.2% at rest and 32.1±3.44% during exercise. Four weeks of CLA supplementation had no significant effect on fatty acid or glycerol metabolism in healthy, weight-stable, adult women.

Estradiol, SHBG and leptin interplay with food craving and intake across the menstrual cycle ☆

OBJECTIVE To understand the association between ovarian hormones, non-acute satiety hormones and craving calorie dense foods in the luteal phase. METHODS 17 premenopausal women, mean age 23.2 y, mean BMI 22.4kg/m(2) with regular menstrual cycles were studied during late follicular (FP) and luteal phases (LP). Estradiol, progesterone, DHEAS, SHBG, insulin and leptin, were measured in fasting samples. The validated Food Craving Inventory was used to record the types of foods volunteers habitually ate - rich in fat, carbohydrate or sweet taste, as well as craved during the LP of their menstrual cycle. RESULTS Estradiol was inversely associated with leptin in FP (r=-0.62, p=0.01). Leptin was inversely associated with habitual intake of sweet foods, in both phases (FP: r=-0.64, p=0.01; LP: r=-0.63, p=0.01). SHBG in LP was positively associated with craving sweet and carbohydrate rich foods. Hierarchical cluster analysis revealed two groups of women, one with high estradiol, high estradiol/leptin ratio, high sweet and carbohydrate cravings (p<0.05); the other group had lower estradiol, lower estradiol/leptin ratio, and reported less craving. CONCLUSIONS The estradiol-leptin axis may be a determinant of luteal phase craving and habitual food intake in menstruating women. CLINICAL TRIAL REGISTRATION NUMBER NCT01407692.

The Effects of Moderate Whole Grain Consumption on Fasting Glucose and Lipids, Gastrointestinal Symptoms, and Microbiota

This study was designed to determine if providing wheat, corn, and rice as whole (WG) or refined grains (RG) under free-living conditions will change parameters of health over a six-week intervention in healthy, habitual non-WG consumers. Measurements of body composition, fecal microbiota, fasting blood glucose, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), and triglycerides were made at baseline and post intervention. Subjects were given adequate servings of either WG or RG products based on their caloric need and asked to keep records of grain consumption, bowel movements, and GI symptoms weekly. After six weeks, subjects repeated baseline testing. Significant decreases in total, LDL, and non-HDL cholesterol were seen after the WG treatments but were not observed in the RG treatment. During Week 6, bowel movement frequency increased with increased WG consumption. No significant differences in microbiota were seen between baseline and post intervention, although, abundance of order Erysipelotrichales increased in RG subjects who ate more than 50% of the RG market basket products. Increasing consumption of WGs can alter parameters of health, but more research is needed to better elucidate the relationship between the amount consumed and the health-related outcome.

In polycystic ovary syndrome, adrenal steroids are regulated differently in the morning versus in response to nutrient intake

OBJECTIVE To investigate adrenal steroid regulation in polycystic ovary syndrome. DESIGN Five-hour oral glucose tolerance test (OGTT) and frequently sampled-intravenous gluclose tolerance test. SETTING University research center. PATIENT(S) Thirty patients. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Anthropometrics, leptin, cortisol, DHEAS, glucose, insulin. RESULT(S) Morning cortisol correlated with sensitivity index (SI, r = .540), DHEAS correlated inversely with age (r = -.6359), body mass index (BMI, r = -.6199), fat mass (r = -0.630), and leptin (r = -0.5676). Between the second and fourth hour of OGTT, cortisol changes (Delta) exhibited three patterns: I, responders (n = 9, Delta: 10.7 +/- 1.0 microg/dL); II, nonresponders (n = 10, Delta: -3.5 +/- 0.6 microg/dL); III, intermediates (n = 11, Delta: 4.3 +/- 1.0 microg/dL). Compared with nonresponders, responders were more obese (BMI: 37.0 +/- 1.6 vs. 31.7 +/- 1.8 kg/m(2)); had higher leptin (28.9 +/- 1.7 vs. 24.1 +/- 1.1 ng/mL), and lower DHEAS (133 +/- 12 vs. 236 +/- 32 ng/mL), higher glucose at 1 h of OGTT (195 +/- 13 vs. 131 +/- 12 mg/dL), higher area under the curve (AUC)(Glucose) (332 +/- 20 vs. 265 +/- 17 mg/dL), higher AUC(Insulin) (244 +/- 50 vs. 125 +/- 30 muU/mL), and lower nadir glucose (61 +/- 2 vs. 70 +/- 2 mg/dL). CONCLUSION(S) Obesity and insulin resistance are associated with lower morning cortisol and DHEAS but increased cortisol and DHEA responses after glucose ingestion. Morning steroid levels may not reflect the day-long exposure.

Structural equation modeling of food craving across the menstrual cycle using behavioral, neuroendocrine, and metabolic factors

OBJECTIVE To identify associations between circulating endocannabinoids and craving during the luteal phase of the menstrual cycle. This report is a secondary analysis of a trial registered in clinicaltrials.gov as NCT01407692. METHODS Seventeen premenopausal women were studied during the follicular and luteal phases of their menstrual cycle. Previously we had reported fasting plasma estradiol, progesterone, leptin associations with luteal phase cravings for carbohydrate, fat, sweet-rich foods, and eating behavior. Here, we measured fasting plasma endocannabinoids (ECs) endocannabinoid-like substances (ECLs), and postprandial metabolic responses to a mixed meal challenge. Structural equation modeling was used to evaluate relationships between measured variables and cravings. RESULTS Oleoylethanolamide (OEA) and postprandial lipids were inversely associated with craving sweet-rich foods, while progesterone was positively associated (RMSEA = 0.041, χ2 p: 0.416 i.e. hypothetical and physiological models not different). OEA, progesterone and disinhibition were positively associated with craving carbohydrates (RMSEA: <0.001, χ2 p: 0.919). ECs and ECLs combined were stronger predictors of craving than clinical metabolic parameters, ECs only, satiety hormones or gonadocorticoids. CONCLUSIONS Our theoretical model suggests that ECs and ECLs influence craving. Since these metabolites can be modulated via dietary fat intake, they could be potential targets to alter menstrual cycle cravings. CLINICAL TRIAL REGISTRATION NUMBER NCT01407692.