Human Nutrition Unit, Department of Biochemistry, University of
Sydney, Sydney, New South Wales 2006, Australia
Leptin is reported to have effects in peripheral
tissues that are independent of its ...central effects on food intake and
body weight. In this study, the acute effects of a single dose of
recombinant mouse leptin on lipid and glucose metabolism in lean and
gold thioglucose-injected obese mice were examined. Changes were
measured 2 h after leptin injection. In lean mice, liver and white
adipose tissue (WAT) lipogenesis was inhibited. The activity of the
pyruvate dehydrogenase complex (PDHCa), the rate-determining step for
glucose oxidation, was reduced in heart, liver, quadriceps muscle, and both brown and white adipose tissues. Muscle and liver glycogen and
liver triglyceride (TG) content was unchanged, but muscle TG was
decreased. In obese mice, liver and WAT lipogenesis was inhibited and
PDHCa reduced in heart and quadriceps muscle. Muscle and liver glycogen
was decreased but not TG. Serum insulin was reduced in obese but not
lean mice. These results are consistent with a role for leptin in the
maintenance of steady-state energy stores by decreasing lipid synthesis
and increasing fat mobilization, with decreased glucose oxidation
occurring as a result of increased fatty acid oxidation.
lipogenesis; pyruvate dehydrogenase complex; fatty acid oxidation
Leptin secretion has been shown to respond acutely to changes in blood glucose and insulin. Nutritional state also has a marked effect on both the level of circulating leptin protein and leptin gene ...expression. The aim of this study was to assess whether the prior nutritional state altered the leptin secretory response to an acute glucose challenge, and to determine potential mechanisms.
Male fed or fasted rats (200-250 g) were administered a single intravenous glucose bolus (1, 4 or 7 g/kg). The serum leptin, glucose, insulin and free fatty acid responses were studied over the following 5 h. The level of leptin gene expression and leptin protein was then determined in the epididymal fat pads, and in fed and fasted untreated rats for basal comparison.
Leptin secretion in response to glucose was suppressed in fasted rats following all glucose doses. The total leptin response was correlated with the total insulin response in all conditions (r = 0.85) and with the glucose response in fed rats (r = 0.69). Both leptin gene expression and leptin protein content were lower in basal fasted rats. Leptin gene expression and leptin protein content still remained lower 5 h following a glucose bolus but there was partial reversal of the effects of fasting following the 7 g/kg glucose dose.
Leptin secretion in response to an intravenous glucose bolus was determined by the insulin response and was significantly suppressed in fasted compared to fed rats. In addition to differences in the total insulin response of the animals, lower leptin responses may be facilitated by lower levels of both leptin gene mRNA and pre-existing leptin protein in epididymal adipose tissue of fasted rats.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
34.
Obesity: epidemiology and possible prevention Caterson, Ian D; Gill, Timothy P
Best Practice & Research Clinical Endocrinology & Metabolism,
12/2002, Volume:
16, Issue:
4
Journal Article
Peer reviewed
Obesity can be defined as the excessive accumulation of fat in adipose tissue, to the extent that health may be impaired. The most widely used measures of total and abdominal adiposity are the body ...mass index and waist circumference. Obesity is now a global public health problem, with about 315 million people world-wide estimated to fall into the WHO-defined obesity categories with a body mass index (BMI) of 30 or above.
The primary causes of the rapid global rise in obesity rates lie in the profound environmental and societal changes now affecting large parts of the world and creating societies in which physical activity is low and the availability of high-fat, energy-dense foods has increased. Strategies aimed at preventing weight gain and obesity have not been successful to date but are likely to be more cost effective, and to have a greater positive impact on long-term control of body weight than treating obesity once it has developed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Objective: Leptin secretion in rats is regulated acutely by nutritional state. Insulin plays an important role in this acute nutritional regulation both directly and indirectly through effects on ...glucose metabolism. The aim of this study was to investigate if the fasting-induced suppression of leptin secretion was reversed by incubation under conditions mimicking nutritional repletion. Design: Leptin secretion and glucose metabolism were measured following incubation with glucose and insulin in adipocytes isolated from fed and fasted rats. Results: Leptin secretion was stimulated by incubation with glucose and insulin in adipocytes isolated from fed but not from fasted rats as was glucose flux through oxidative and lipogenic pathways. Ob expression and intracellular leptin content were decreased in adipocytes isolated from fasted rats throughout the whole incubation period. Suppression of glucose metabolism with cytochalasin B was accompanied by suppression of leptin secretion. The amount of leptin secretion correlated with the glucose incorporated into lipid under insulin-stimulated conditions. Conclusions: It is proposed that glucose incorporation into lipid, at least during insulin-stimulated conditions, reflects the metabolic status of the adipocyte and may be a more important regulator of leptin production and secretion than circulating glucose or insulin levels.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To assess the effect of a 3 month behaviour modification weight management programme on self-efficacy and anthropometric variables among obese women seeking treatment at an obesity management clinic ...and to compare self-efficacy among these obese women to non-obese women.
Cross sectional.
A total of 161 non-obese (BMI 22.6+/-2.9 kg/m(2)) and 138 obese (BMI 37.7+/-5.8 kg/m(2)) women of similar age.
Self-efficacy in relation to eating was assessed by the Weight Efficacy Lifestyle (WEL) questionnaire. Demographic information was obtained by interview and questionnaire in the obese and by questionnaire in the non-obese. Anthropometric measurements were obtained by direct measure in the obese and BMI was calculated from self-reported weight and height in the non-obese.
At entry to the programme obese women scored significantly less (P<0.0001) than non-obese women on the WEL (99.4+/-34.1 vs 139.0+/-24.9). Women who completed the programme (n=65) demonstrated a decrease in waist circumference of 3.9+/-5.3 cm, a 10.0+/-11.5% loss of excess weight and a significant improvement in total WEL score from 106.0+/-30.3 to 126.5+/-28.4.
Improvements in some dimensions of self-efficacy among obese women were of sufficient magnitude to attain scores similar to women of a normal weight. The WEL questionnaire may provide an additional measure of success as well as provide positive feedback and encouragement to the client.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Skeletal muscle plays a major role in insulin‐stimulated glucose disposal. This paper reviews the range of evidence in humans and experimental animals demonstrating close associations between insulin ...action and two major aspects of muscle morphology: fatty acid composition of the major structural lipid (phospholipid) in muscle cell membranes and relative proportions of major muscle fiber types. Workin vitro andin vivo in both rats and humans has shown that incorporation of more unsaturated fatty acids into muscle membrane phospholipid is associated with improved insulin action. As the corollary, a higher proportion of saturated fats is linked to impairment of insulin action (insulin resistance). Studiesin vitro suggest a causal relationship. Among polyunsaturated fatty acids (PUFA) there is some, but not conclusive, evidence that ω‐3 (n−3) PUFA may play a particular role in improving insulin action; certainly a high n−6/n−3 ratio appears deleterious. In relation to fiber type, the more highly oxidative, insulin‐sensitive type 1 and type 2a fibers have a higher percentage of unsaturated fatty acids, particularly n−3, in their membrane phospholipid, compared to the insulin‐resistant, glycolytic, type 2b fibers. These variables, however, can be separated and may act in synergy to modulate insulin action. It remains to establish whether lifestyle (e.g., dietary fatty acid profile and physical activity), genetic predisposition, or a combination are the prime determinants of muscle morphology (particularly membrane lipid profile) and hence insulin action.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Aim: To investigate the efficacy of motivational enhancement strategies integrated within a standard lifestyle modification program for the maintenance of weight loss and improved psychosocial ...functioning of obese adults.
Methods: Twenty‐two obese adults completed 20 sessions of a motivationally informed cognitive behavioural treatment for weight loss and maintenance. Treatment outcome measures included anthropometrics, obesity‐specific quality of life, impulsive eating tendencies, body dissatisfaction, mood disturbance and maladaptive cognitions.
Results: At post‐treatment, there was a significant decrease in body weight (123.04 ± 22.06 vs. 116.84 ± 23.53, p < 0.001) with no significant change by the 12‐month follow‐up. Patients also reported significant improvements in obesity‐related quality of life, impulsive eating tendencies, body dissatisfaction and maladaptive cognitions at post‐treatment that were maintained at the 1‐year follow‐up.
Conclusions: The implementation of motivational enhancement strategies within a cognitive behavioural program results in sustained weight loss that compares favourably to previous lifestyle modification programs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To investigate the fibre type composition of skeletal muscle in infants and young children and to compare the findings to an adult population. To relate the fibre type profile of skeletal muscle in ...adults to measures of adiposity.
Cross-sectional studies of skeletal muscle fibre composition in infants and adults with measures of adiposity in the adults.
21 healthy infants and young children (age: 3-21 months) and 40 healthy adult Australian Caucasians (age: 26-62 y; BMI: 18-48 kg/m2).
Skeletal muscle fibre type composition (by myosin ATPase method) and relative body fatness (BMI, waist circumference and waist/hip ratio (WHR)).
Infants and young children had significantly lesser proportions of glycolytic Type 2b fibres (6.2 +/- 1.1%; range 0.3-18.9%) compared with adults (20.5 +/- 1.6%; range 4.9-36.0%) (p < 0.0001). The percentage of Type 2b fibres was directly related to BMI (r = 0.44, p = 0.02), waist circumference (r = 0.49, p = 0.009) and WHR (r = 0.44, p = 0.02) in adults. A significant, direct relationship was also found between the proportion of glycolytic Type 2b fibres and age in the adults (r = 0.45, p = 0.01).
Skeletal muscle fibre type composition is different in infants and adults and there is an age-dependent increase in Type 2b fibres over the lifespan. An increased proportion of glycolytic Type 2b fibres is associated with obesity in adults. Results support a gene-environment interaction on fibre type composition in human skeletal muscle.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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