Negative regulation of leptin by chronic high-glycemic index starch diet

Starch intake, amylase gene copy number variation, plasma proteins, and risk of cardiovascular disease and mortality

BACKGROUND

Salivary amylase, encoded by the AMY1 gene, initiate the digestion of starch. Whether starch intake or AMY1 copy number is related to disease risk is currently rather unknown. The aim was to investigate the association between starch intake and AMY1 copy number and risk of cardiovascular disease (CVD) and mortality and whether there is an interaction. In addition, we aim to identify CVD-related plasma proteins associated with starch intake and AMY1 copy number.

METHODS

This prospective cohort study used data from 21,268 participants from the Malmö Diet and Cancer Study. Dietary data were collected through a modified diet history method and incident CVD and mortality were ascertained through registers. AMY1 gene copy number was determined by droplet digital polymerase chain reaction, a risk score of 10 genetic variants in AMY1 was measured, and a total of 88 selected CVD-related proteins were measured. Cox proportional hazards regression was used to analyze the associations of starch intake and AMY1 copy number with disease risk. Linear regression was used to identify plasma proteins associated with starch intake and AMY1 copy number.

RESULTS

Over a median of 23 years' follow-up, 4443 individuals developed CVD event and 8125 died. After adjusting for potential confounders, a U-shape association between starch intake and risk of CVD (P-nonlinearity = 0.001) and all-cause mortality (P-nonlinearity = 0.03) was observed. No significant association was found between AMY1 copy number and risk of CVD and mortality, and there were no interactions between starch intake and AMY1 copy number (P interaction > 0.23). Among the 88 plasma proteins, adrenomedullin, interleukin-1 receptor antagonist protein, fatty acid-binding protein, leptin, and C-C motif chemokine 20 were associated with starch intake after adjusting for multiple testing.

CONCLUSIONS

In this large prospective study among Swedish adults, a U-shaped association between starch intake and risk of CVD and all-cause mortality was found. Several plasma proteins were identified which might provide information on potential pathways for such association. AMY1 copy number was not associated with CVD risk or any of the plasma proteins, and there was no interaction between starch intake and AMY1 copy number on disease risk.

The association between dietary patterns with severity of coronary artery stenosis, serum leptin-to-adiponectin ratio, and some related risk factors in patients with coronary artery disease

Background

This research aimed to investigate the association between dietary patterns with severity of coronary artery stenosis, serum leptin-to-adiponectin ratio, and some related risk factors in patients with coronary artery disease referred for coronary angiography.

Methods

This cross-sectional study was carried out on 191 men patients with known coronary disease aged 40-70 years whom were admitted to angiography ward of Ahvaz teaching hospital, Ahvaz, Iran. Dietary patterns were investigated using 161-item semi-quantitative food frequency questionnaire. Anthropometric indices; blood pressure; serum levels of adiponectin and leptin, blood levels of glucose, total cholesterol, HDL-C, LDL-C, and triglycerides were measured. Patients were categorized based on the severity of coronary artery disease [number of vessel involved-single (VD1), double (VD2), triple (VD3)].

Results

Three major dietary patterns were recognized using a factor analysis approach: western, healthy, and traditional patterns. Linear regression analysis demonstrated that there was a negative association between healthy dietary pattern with LDL-C, total cholesterol, and triglycerides. This dietary pattern was positively related to HDL-C. Both traditional and western dietary patterns were related to fasting blood glucose level and lipid profile. General obesity was positively associated with traditional and western dietary patterns. There was a positive relationship between central obesity with traditional and western dietary patterns, but a negative association was reported between the healthy dietary pattern and central obesity. Traditional and western dietary patterns demonstrated a significant positive relationship with serum leptin levels and ratio of L/A, and an inverse relationship with adiponectin. Healthy dietary pattern had a significant negative association with serum leptin levels and ratio of L/A. Healthy dietary pattern was negatively related to the severity of vessel stenosis. Patients in the third quartile of healthy dietary pattern were less likely to have vessel stenosis (OR = 43%, 95% CI: 0.07-0.87).

Conclusions

The findings show that adherence to a healthy dietary pattern was negatively associated with coronary artery stenosis and its related risk factors. However, adherence to western and traditional dietary patterns was positively related to coronary artery disease risk factors.

Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations

While dietary factors are important modifiable risk factors for type 2 diabetes (T2D), the causal role of carbohydrate quality in nutrition remains controversial. Dietary glycemic index (GI) and glycemic load (GL) have been examined in relation to the risk of T2D in multiple prospective cohort studies. Previous meta-analyses indicate significant relations but consideration of causality has been minimal. Here, the results of our recent meta-analyses of prospective cohort studies of 4 to 26-y follow-up are interpreted in the context of the nine Bradford-Hill criteria for causality, that is: (1) Strength of Association, (2) Consistency, (3) Specificity, (4) Temporality, (5) Biological Gradient, (6) Plausibility, (7) Experimental evidence, (8) Analogy, and (9) Coherence. These criteria necessitated referral to a body of literature wider than prospective cohort studies alone, especially in criteria 6 to 9. In this analysis, all nine of the Hill’s criteria were met for GI and GL indicating that we can be confident of a role for GI and GL as causal factors contributing to incident T2D. In addition, neither dietary fiber nor cereal fiber nor wholegrain were found to be reliable or effective surrogate measures of GI or GL. Finally, our cost–benefit analysis suggests food and nutrition advice favors lower GI or GL and would produce significant potential cost savings in national healthcare budgets. The high confidence in causal associations for incident T2D is sufficient to consider inclusion of GI and GL in food and nutrient-based recommendations.

Effects of sprouted and fermented quinoa (Chenopodium quinoa) on glycemic index of diet and biochemical parameters of blood of Wistar rats fed high carbohydrate diet

Sprouted and fermented foods have shown hypoglycemic effects on humans and animals, by reducing concentrations of soluble carbohydrates, and increasing dietary fiber and resistant starch content. In this study, diets with high levels of simple carbohydrates supplemented with toasted quinoa flour, sprouted and toasted quinoa flour, fermented and toasted quinoa flour or sprouted/fermented and toasted quinoa flour were given to Wistar rats. During the experiment, the glycemic index (GI) of the diets were measure and, at the end of 47 days of feeding, the effects of the diets on physical and biochemical parameters of the animals were evaluated. Results indicated that the processes of sprouting and/or fermentation potentiate the ability of quinoa to reduce GI of diets with high levels of simple carbohydrates. Moreover, food intake, blood glucose and lipid levels, and accumulation of epididymal adipose tissue were reduced in rats fed diets supplemented with quinoa. These effects may be due to the nutritional composition of the supplemented diets, besides the chemical changes promoted by processing quinoa. These results are particularly relevant once sprouted and fermented quinoa could be an alimentary source of interest, especially for disease risk prevention such as diabetes, obesity and dyslipidemias.

Leptin, Leptin Soluble Receptor, and the Free Leptin Index following a Diet and Physical Activity Lifestyle Intervention in Obese Males and Females

Leptin (LEP) is associated with appetite regulation and metabolism. Concentration is linear with adiposity, suggesting LEP resistance. LEP circulates freely and bound with its soluble receptor (sOB-r); the ratio is the free leptin index (FLI), an index of leptin resistance; lower FLI suggests reduced biological action. Purpose. The aim was to determine the effect of changes in adipose tissue distribution on LEP, sOB-r, and FLI following 6 months (6 M) of a diet/exercise weight loss program (WLP). In addition, we aim to identify predictors of the FLI. Methods. 6 M WLP consisted of diet/lifestyle interventions following ADA guidelines. Body composition was assessed by DXA. LEP and sOB-r analysis were done via ELISA. Results. 10 adults completed the WLP. Significant reductions were seen in total fat percentage (% fat), nontrunk fat, (NTF), and trunk fat (TF) from base to 3 m and 6 M (p ≤ 0.05). The FLI were reduced at 3 M and 6 M for males and 6 M for females. Total body fat and body weight predicted the FLI in both sexes. Conclusions. LEP and FLI reductions following 6 M of WLP were achieved independent of sOB-r changes. We also demonstrate that the FLI can be predicted noninvasively through total fat mass and body weight in kilograms.

Association between dietary patterns and serum leptin-to-adiponectin ratio in apparently healthy adults

OBJECTIVE

Dietary patterns reflect diet and nutritional habits of individuals in a society. Various dietary patterns could influence leptin and adiponectin secretion from adipose tissue. These hormones are associated with metabolic diseases. It is suggested that the leptin-to-adiponectin (L/A) ratio might be a more useful diagnostic marker in predicting chronic diseases than leptin and adiponectin separately. The aim of this study was to investigate the association between various dietary patterns and L/A ratio in Iranian adults.

METHODS

This cross-sectional study was conducted on 150 apparently healthy subjects aged 25-50 years in Tabriz, Iran. Dietary patterns were determined using 132-item semiquantitative food frequency questionnaire on a 5-point scale. Weight, height, waist circumference (WC), as well as fasting serum leptin and adiponectin levels were measured to assess the association between dietary patterns and L/A ratio.

RESULTS

Four major dietary patterns were identified using a factor analysis approach: Western, healthy, mixed, and traditional dietary patterns. Linear regression analysis showed that a Western dietary pattern was negatively associated with serum adiponectin concentration, even after adjusting for the confounders (r = -0.19, p = 0.02). No statistically significant associations were found between any dietary pattern and leptin (r = -0.14, p = 0.06) or L/A ratio (r = -0.10, p = 0.09).

CONCLUSION

Our findings indicate an inverse association between a Western dietary pattern and serum adiponectin levels but not for serum leptin or L/A ratio.

Antidiabetic potential of commonly consumed legumes: a review

Over the last few decades, lifestyle changes have resulted in a drastic increase in the incidence of diabetes all over the world, especially in the developing countries. Oral hypoglycemic agents and insulin form the mainstay in controlling diabetes, but they have prominent side effects and fail to significantly alter the course of diabetic complications. Appropriate diet and exercise programs that form a part of lifestyle modifications have proven to be greatly effective in the management of this disease. Dietary therapy is showing a bright future in the prevention and treatment of diabetes. Legumes, owing to their high nutritive value, are increasingly being used in dietetic formulations in the treatment and prevention of diabetes on account of their antidiabetic potential. Given this background, this paper reviews the glucose- and lipid-lowering action possessed by various commonly consumed legumes through several animal and human studies. It is concluded that the various legumes not only have varying degrees of antidiabetic potential but are also beneficial in decreasing the risk factors for cardiovascular and renal disease.

Glycemic load is associated with oxidative stress among prevalent maintenance hemodialysis patients

BACKGROUND

High glycemic index (GI) and glycemic load (GL) are associated with increased levels of oxidative stress and systemic inflammation in the general population. Maintenance hemodialysis (MHD) patients are known to have excessive oxidative stress burden and inflammation. In this study, we examined the relationship between dietary GI or GL and markers of oxidative stress or inflammation among prevalent MHD patients.

METHODS

A registered dietitian obtained GI, GL and other dietary data from 58 MHD patients. Two separate 24-h diet recalls (a hemodialysis day and a non-hemodialysis day) were analyzed using the Nutrition Data System for Research (NDS-R) software. Plasma or serum concentrations of F2-isoprostanes, high sensitivity C-reactive protein (hsCRP), leptin and adiponectin (ADPN) were measured in fasting state. Fat mass was measured by dual-energy X-ray absorptiometry (DEXA). Cross-sectional associations between GI, GL and markers of interest were examined by multiple regression analysis with adjustment for potential covariates.

RESULTS

Mean (±SD) age, body mass index (BMI) and total trunk fat were 47 ± 12 years, 29.5 ± 6.8 kg/m(2) and 16.4 ± 8.8 kg, respectively. Dietary GI was associated with trunk fat (r = -0.182, P = 0.05) but not with F2-isoprostanes and hsCRP. In contrast, GL was significantly associated with F2-isoprostanes (P = 0.002), in unadjusted analysis, which remained in adjusted analyses, adjusting for age and sex (P = 0.005), and after adjusting for BMI, trunk fat and waist/hip ratio (P = 0.004). Addition of leptin or ADPN did not alter the significance of the association. GL also correlated with hsCRP (P = 0.03), but this association was modified by BMI and trunk fat.

CONCLUSIONS

Dietary GL is significantly associated with markers of oxidative stress and inflammation among prevalent MHD patients, independent of the body composition and adipocytokines. These data indicate the importance of the contents of dietary nutrient intake composition and its potential role in determining the metabolic disturbances in MHD patients.

Dietary glycemic index/load and peripheral adipokines and inflammatory markers in elderly subjects at high cardiovascular risk

BACKGROUND AND AIMS

Epidemiological and clinical studies suggest that low-glycemic index diets could protect against weight gain. However, the relationship between these diets and adipokines or inflammatory markers is unclear. In the present study we examine how the dietary glycemic index (GI) and dietary glycemic load (GL) are associated with several adipokines and related metabolic risk markers of obesity and diabetes in a cross-sectional and longitudinal manner.

METHODS AND RESULTS

511 elderly community-dwelling men and women at high cardiovascular risk were recruited for the PREDIMED trial. Dietary data were collected at baseline and after 1 year of follow-up. The GI and GL were calculated. Plasma leptin, adiponectin and other metabolic risk markers were measured at baseline and after 1 year. At baseline, subjects in the highest quartiles of GI showed significantly higher levels of TNF and IL-6 than those in the lowest quartiles. Dietary GI index was negatively related to plasma leptin and adiponectin levels. After 1 year of follow-up, subjects with a higher increase in dietary GI or GL showed a greater reduction in leptin and adiponectin plasma levels. There was no association between GI or GL and the other metabolic markers measured.

CONCLUSION

Our results suggest that the consumption of high-GI or high-GL diets may modulate plasma concentrations of leptin and adiponectin, both adipostatic molecules implicated in energy balance and cardiometabolic risk.

Sleep deprivation is associated with lower diet quality indices and higher rate of general and central obesity among young female students in Iran

OBJECTIVES

Short sleep duration and low diet quality are associated with weight gain. However, little is known about the relationship between sleep duration and the quality of diets. Therefore, we aimed to compare the diet quality indices and anthropometric measures between short and longer sleepers.

METHODS

This cross-sectional study consisted of 410 female youths who were chosen among students of Isfahan University of Medical Sciences based on stratified random sampling method. Dietary intake assessment was done using a semiquantitative validated food frequency questionnaire. Sleep duration was estimated using self-reported nocturnal sleep duration by each person. Anthropometric measures were done using standard protocols. Diet quality indices (including dietary energy density, dietary diversity scores, healthy eating index, nutrient adequacy ratio, and mean adequacy ratio) were calculated using the standard definition.

RESULTS

Subjects who slept less than 6 h/d were more likely to be overweight and obese (P = 0.0001) and also abdominally obese (P = 0.03). They also consumed more dietary energy (2406 ± 825 versus 2092 ± 700 kcal/d; P = 0.01, respectively) and carbohydrates (58.1 ± 16.2% versus 51.6 ± 10.3%; P = 0.03) but a lower amount of fiber (12 ± 7 versus 18 ± 7 g/d; P = 0.04), fruits (2.4 ± 0.6 versus 3.1 ± 0.7 servings/d; P = 0.04), whole grains (0.9 ± 0.1 versus 1.3 ± 0.1 servings/d; P = 0.04), and beans (0.3 ± 0.1 versus 0.8 ± 0.1 servings/d; P = 0.04). All diet quality indices were significantly lower among short sleepers (P < 0.05), apart from dietary energy density, which did not differ significantly (P = 0.8).

CONCLUSION

Our findings confirm the association of short sleep duration and obesity in young female youths. It might be derived from lower diet quality among short sleepers more than longer sleepers.

The importance of dietary modulation of cAMP and insulin signaling in adipose tissue and the development of obesity

Adipose tissue plays a pivotal role in whole body energy homeostasis. In this review, we summarize knowledge of the seemingly paradoxical roles of insulin and cyclic adenosine monophosphate (cAMP) signaling in adipocyte differentiation and function, emphasizing the interplay between the two branches of cAMP signaling, the canonical protein kinase A-dependent pathways and the novel exchange protein activated by cAMP (Epac)-dependent pathways, and insulin signaling. We discuss how macronutrients via changes in the balance between insulin- and cAMP-dependent signaling can affect the development of obesity by changing energy expenditure and/or feed efficiency. We review results demonstrating how the balance between different classes of carbohydrates and proteins modulates the obesigenic action of saturated as well as unsaturated fatty acids pointing to insulin as a key determinant in the regulation of the metabolic/regulatory action of both n-3 and n-6 polyunsaturated fatty acids.

Effects of a high-fat, low- versus high-glycemic index diet: retardation of insulin resistance involves adipose tissue modulation

Beneficial effects of low glycemic index (GI) diets in rodents have been studied using healthy low-fat diets, while the effects might be different on high-fat diets inducing progression of insulin resistance. We fed C57BL/6J male mice high-fat low/high-GI (LGI/HGI) diets for 13 wk. Glucose and insulin tolerance and serum substrates, including adipokines, were measured longitudinally. The LGI group showed a significantly higher glucose tolerance from wk 2 onwards, which was supported by lower serum insulin and free fatty acids levels at 8 wk, and a tendency for lower leptin levels, while resistin levels remained similar. At 11 wk, when differences in serum resistin started to increase, differences in serum insulin were diminished. Although food intake was similar throughout the study, body weights and epididymal adipose tissue mass became significantly lower in the LGI group at necropsy. Several serum substrates and adipose tissue leptin mRNA levels, as analyzed by Q-PCR, were, again, significantly lower, whereas adiponectin mRNA levels were higher. Taken together, an LGI high-fat diet maintains higher glucose tolerance and insulin sensitivity via adipose tissue modulation solely because of a difference in the type of carbohydrate, supporting a nutritional approach in the fight against insulin resistance.

Índice glicêmico: uma abordagem crítica acerca de sua utilização na prevenção e no tratamento de fatores de risco cardiovasculares

As doenças cardiovasculares são consideradas um grande problema de saúde pública, uma vez que são a principal causa de morte no Brasil e no mundo. Essas doenças possuem etiologia multifatorial. Além da susceptibilidade genética, outros fatores, tais como idade e presença de hipertensão arterial, dislipidemias, obesidade, diabetes mellitus, inatividade física e alguns hábitos alimentares inadequados, são considerados importantes fatores de risco para o desenvolvimento de doenças cardiovasculares. O elevado consumo de carboidratos tem sido associado ao aumento da obesidade, às dislipidemias, à intolerância à glicose/diabetes mellitus e à resistência insulínica, estando, dessa forma, entre os fatores de risco das doenças cardiovasculares. Entretanto, existem controvérsias acerca da influência da qualidade do carboidrato ingerido no desenvolvimento de tais doenças, independentemente da quantidade ingerida. O índice glicêmico é um indicador da qualidade do carboidrato ingerido. Sua utilidade em condições de vida livre tem sido questionada, devido à interferência de vários fatores, os quais são difíceis de serem controlados sob tais condições. Este trabalho objetivou analisar criticamente os estudos que avaliaram o efeito do índice glicêmico dos alimentos na manifestação de doenças cardiovasculares e seus fatores de risco.

A high glycemic meal suppresses the postprandial leptin response in normal healthy adults

BACKGROUND/AIMS

To evaluate the metabolic effects of meals with varying glycemic index (GI).

METHODS

We measured the glucose, insulin and leptin responses to two contrasting breakfast cereals in a group of 10 young healthy volunteers. Meals were provided on two separate occasions in random order after a 12-hour overnight fast, and consisted of 50 g of available carbohydrate from either Corn Flakes (Kellogg's), or Fiber One (General Mills). Blood samples were obtained at rest, and 30, 60, 90 and 120 min after eating. The GI was calculated from the glucose response to the test meal normalized against a 50 g oral glucose load.

RESULTS

The GI for Corn Flakes was 125 +/- 17 units and 49 +/- 8 units for Fiber One(R). These meals were classified as high GI and low GI, respectively, and were significantly different from each other (p < 0.0003). The area under the insulin response curve (AUC) following the low glycemic meal was significantly attenuated compared to the high glycemic meal (14,064 +/- 2,694 vs. 6,828 +/- 1,182 pmol/l.min, p < 0.02). The leptin AUC revealed that circulating leptin was suppressed by the high glycemic meal compared to the low (3.1 +/- 1.5 vs. 9.6 +/- 3.6 ng/ml.min, p < 0.04).

CONCLUSIONS

Lower insulin and higher leptin suggests that low glycemic meals promote a postprandial metabolic milieu that is favorable for reduced food consumption; this may be advantageous in the control of obesity and related disorders including insulin resistance and type 2 diabetes.

New legume sources as therapeutic agents

This review evaluates the potential health benefits of three legume sources that rarely appear in Western diets and are often overlooked as functional foods. Fenugreek (Trigonella foenum graecum) and isolated fenugreek fractions have been shown to act as hypoglycaemic and hypocholesterolaemic agents in both animal and human studies. The unique dietary fibre composition and high saponin content in fenugreek appears to be responsible for these therapeutic properties. Faba beans (Vicia faba) have lipid-lowering effects and may also be a good source of antioxidants and chemopreventive factors. Mung beans (Phaseolus aureus, Vigna radiatus) are thought to be beneficial as an antidiabetic, low glycaemic index food, rich in antioxidants. Evidence suggests that these three novel sources of legumes may provide health benefits when included in the daily diet.

Carbohydrate fractions of legumes: uses in human nutrition and potential for health

Starch and fibre can be extracted, using wet or dry processes, from a variety of grain legumes and used as ingredients for food. alpha-Galactosides can be isolated during wet processes from the soluble extract. Starch isolates or concentrates are mostly produced from peas, whereas dietary fibre fractions from peas and soyabean are commercially available. The physico-chemical characteristics of fibre fractions very much depend on their origin, outer fibres being very cellulosic whereas inner fibres contain a majority of pectic substances. Inner fibres are often used as texturing agents whereas outer fibres find their main uses in bakery and extruded products, where they can be introduced to increase the fibre content of the food. Most investigations on impacts on health have been performed on soyabean fibres. When positive observations were made on lipaemia, glucose tolerance or faecal excretion, they were unfortunately often obtained after non-realistic daily doses of fibres. Legume starches contain a higher amount of amylose than most cereal or tuber starches. This confers these starches a lower bioavailability than that of most starches, when raw or retrograded. Their low glycaemic index can be considered as beneficial for health and especially for the prevention of diseases related to insulin resistance. When partly retrograded, these starches can provide significant amount of butyrate to the colonic epithelium and may help in colon cancer prevention. alpha-Galactosides are usually considered as responsible for flatus but their apparent prebiotic effects may be an opportunity to valorize these oligosaccharides.

Health benefits of low glycaemic index foods, such as pulses, in diabetic patients and healthy individuals

The present paper covers the health benefits of low glycaemic index foods, such as pulses. Nutritional factors potentially play a crucial role in health and disease. A low-fat, high-carbohydrate diet is often recommended as a part of a healthy life-style. Historical works have shown that carbohydrate foods differ in their ability to affect post-ingestive glycaemia. The glycaemic index concept allows a ranking of carbohydrate-rich foods in terms of their blood glucose raising potential. Pulses are foods with very low glycaemic index values. Numerous studies have documented the health benefits that can be obtained by selecting foods of low glycaemic index. These benefits are of crucial importance in the dietary treatment of diabetes mellitus: glycaemic control is improved as well as several metabolic parameters, such as blood lipids. The results of human studies have been confirmed by animal experiments in the field of diabetes. Diets with low glycaemic index value improve the prevention of coronary heart disease in diabetic and healthy subjects. In obese or overweight individuals, low-glycaemic index meals increase satiety and facilitate the control of food intake. Selecting low glycaemic index foods has also demonstrated benefits for healthy persons in terms of post-prandial glucose and lipid metabolism. Several public health organizations have recently integrated consideration of the glycaemic index in their nutritional recommendations for patients with metabolic diseases and for the general population.

Should obese patients be counselled to follow a low-glycaemic index diet? No

In diabetes research the glycaemic index (GI) of carbohydrates has long been recognized and a low GI is recommended. The same is now often the case in lipid research. Recently, a new debate has arisen around whether a low-GI diet should also be advocated for appetite- and long-term body weight control. A systematic review was performed of published human intervention studies comparing the effects of high- and low-GI foods or diets on appetite, food intake, energy expenditure and body weight. In a total of 31 short-term studies (< 1 d), low-GI foods were associated with greater satiety or reduced hunger in 15 studies, whereas reduced satiety or no differences were seen in 16 other studies. Low-GI foods reduced ad libitum food intake in seven studies, but not in eight other studies. In 20 longer-term studies (< 6 months), a weight loss on a low-GI diet was seen in four and on a high-GI diet in two, with no difference recorded in 14. The average weight loss was 1.5 kg on a low-GI diet and 1.6 kg on a high-GI diet. To conclude, there is no evidence at present that low-GI foods are superior to high-GI foods in regard to long-term body weight control. However, the ideal long-term study where ad libitum intake and fluctuations in body weight are permitted, and the diets are similar in all aspects except GI, has not yet been performed.

The effect of adrenalectomy on leptin levels and some metabolic parameters in rats with diet-induced obesity

Recently, there has been many investigations on the relationship between leptin and obesity, which is the main health problem in developed countries. In some reports, it has been claimed that the adrenalectomy has lead to weight loss and thus prevented obesity induced in rodents in various ways. It has also been accepted that diet-induced obesity in animals is very similar to obesity in humans beings. In this study, obesity has been developed with high-calorie diet given for 8 weeks in Sprague-Dawley rats. Then, it has been investigated how leptin and some metabolic parameters change in blood samples obtained from rats 15 d after adrenalectomy. Leptin levels was determined with Radio Immun Assay (RIA, Linco Research Co) method. Our study showed that, there were statistically significant increases in leptin (p<0.001), glucose (p<0.05), triglyceride (p<0.01) levels in diet-induced obese rats (n=19) when compared with the findings of control rats, lean ones (n=16), (Tables 3, 4). Adrenalectomy led to decreased serum leptin (p<0.001) and triglyceride (p<0.01) levels both in the obese and lean rats (Table 5). As a conclusion, it could be claimed that the decrease in leptin levels may be attributed to reduced adipose tissue due to adrenalectomy. On the other hand, the decreases in glucose and triglyceride levels might be the consequence of reduced lipogenesis and impaired gluconeogenesis with the effect of adrenalectomy. It was concluded that adrenalectomy might prevent obesity by affecting leptin and intermediate metabolism.