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Biomedical subjects

H A Koistinen

Publications and source records attributed to H A Koistinen.

At least 19 recordsLinked to original sources
PubMed2005

Paradoxical rise in serum adiponectin concentration in the face of acid-induced insulin resistance 13-cis-retinoic.

AIMS/HYPOTHESIS: We previously reported that treatment of acne with 13-cis-retinoic acid causes insulin resistance and disturbances in lipid metabolism resembling those of the insulin-resistance syndrome. It is not known whether this is associated with alterations in the concentrations of serum adiponectin, an insulin-sensitising hormone secreted by adipocytes. MATERIALS AND METHODS: Eleven men (age 24+/-2 years, BMI 22.1+/-0.9 kg/m(2)) received 13-cis-retinoic acid (Roaccutan) treatment for acne for an average of 5 months. The insulin sensitivity of the subjects and concentrations of serum adiponectin were measured before, during and 1 month after the treatment by a euglycaemic-hyperinsulinaemic clamp and ELISA, respectively. RESULTS: There was a reversible reduction in whole-body insulin sensitivity during therapy with 13-cis-retinoic acid. This was associated with a transient 34% increase in serum adiponectin concentration (from 5.3+/-0.9 to 7.1+/-1.2 mug/ml, p<0.05), with a return to pretreatment levels by 1 month after the end of therapy. In the pretreatment study, as well as in the study performed 1 month after the end of therapy, there was a small yet significant decrease in serum adiponectin concentration during a 4-h euglycaemic-hyperinsulinaemic clamp. This decrease was not observed in the clamp performed during treatment with 13-cis-retinoic acid. CONCLUSIONS/INTERPRETATION: There is a paradoxical increase in fasting serum adiponectin concentration during the 13-cis-retinoic acid-induced reduction in insulin sensitivity.

Acne Vulgaris↗
PubMed2003

Aberrant p38 mitogen-activated protein kinase signalling in skeletal muscle from Type 2 diabetic patients.

AIMS/HYPOTHESIS: p38 mitogen activated protein kinase (MAPK) is generally thought to facilitate signal transduction to genomic, rather than metabolic responses. However, recent evidence implicates a role for p38 MAPK in the regulation of glucose transport; a site of insulin resistance in Type 2 diabetes. Thus we determined p38 MAPK protein expression and phosphorylation in skeletal muscle from Type 2 diabetic patients and non-diabetic subjects. METHODS: In vitro effects of insulin (120 nmol/l) or AICAR (1 mmol/l) on p38 MAPK expression and phosphorylation were determined in skeletal muscle from non-diabetic (n=6) and Type 2 diabetic (n=9) subjects. RESULTS: p38 MAPK protein expression was similar between Type 2 diabetic patients and non-diabetic subjects. Insulin exposure increased p38 MAPK phosphorylation in non-diabetic, but not in Type 2 diabetic patients. In contrast, basal phosphorylation of p38 MAPK was increased in skeletal muscle from Type 2 diabetic patients. CONCLUSION/INTERPRETATION: Insulin increases p38 MAPK phosphorylation in skeletal muscle from non-diabetic subjects, but not in Type 2 diabetic patients. However, basal p38 MAPK phosphorylation is increased in skeletal muscle from Type 2 diabetic patients. Thus, aberrant p38 MAPK signalling might contribute to the pathogenesis of insulin resistance.

Aminoimidazole Carboxamide↗
PubMed2002

Regulation of glucose transport in human skeletal muscle.

Glucose transport, the rate limiting step in glucose metabolism in skeletal muscle, is mediated by insulin-sensitive glucose transporter 4 (GLUT4) and can be activated in skeletal muscle by two separate and distinct signalling pathways: one stimulated by insulin and the second by muscle contractions. Skeletal muscle is the principal tissue responsible for insulin-stimulated glucose disposal and thus the major site of peripheral insulin resistance. Impaired glucose transport in skeletal muscle leads to impaired whole body glucose uptake, and contributes to the pathogenesis of Type 2 diabetes mellitus. A combination of genetic and environmental factors is likely to contribute to the pathogenesis of Type 2 diabetes mellitus; however, the primary defect is still unknown. Intense efforts are underway to define the molecular mechanisms that regulate glucose metabolism in insulin sensitive tissues. This review will present our current understanding of mechanisms regulating glucose transport in skeletal muscle in humans. Elucidation of the pathways involved in the regulation of glucose homeostasis will offer insight into the pathogenesis of insulin resistance and Type 2 diabetes mellitus and may lead to the identification of biochemical entry points for drug intervention to improve glucose homeostasis.

AMP-Activated Protein Kinase Kinases↗
PubMed2001

Concentration of the complement activation product, acylation-stimulating protein, is related to C-reactive protein in patients with type 2 diabetes.

Type 2 diabetes is characterized by increased acute phase serum proteins. We wanted to study how these proteins are related to complement activation in type 2 diabetes and how improvement of glycemic control affects them or complement activation. A total of 29 type 2 diabetic patients (age, 55.2 +/- 1.8 years, glycosylated hemoglobin [HbA(1c)] 8.9% +/- 0.2%, body mass index [BMI] 30.9 +/- 0.8 kg/m(2), duration 5.9 +/- 1.3 years) participated in the study. They were previously treated either with diet alone or in combination with 1 oral antihyperglycemic medication. After a period of at least 4 weeks run-in on diet only, the patients were randomized to pioglitazone, glibenclamide, or placebo. Blood samples were taken before the treatments and at the end of the 6-month therapy. Basal C-reactive protein (CRP) level was related to acylation-stimulating protein (ASP) concentration (r =.55, P <.01), and many acute phase serum protein concentrations were associated with each other. The treatment reduced HbA(1c) level in the pioglitazone (from 9.1 +/- 0.3% to 8.0 +/- 0.5%, P <.05) and glibenclamide (from 8.9 % +/- 0.3% to 7.7% +/- 0.2%, P <.05) groups. Glibenclamide treatment was associated with a reduction in alpha-1-antitrypsin (P <.05), ceruloplasmin (P <.01), and complement C3 protein (C3) (P <.05). Although ASP did not change significantly in any of the treatment subgroups, in the whole patient population, the change in HbA(1c) during the treatments correlated positively with the change in ASP, (r =.43, P <.05). The changes in many acute phase serum proteins and ASP were related to each other. In conclusion, (1) inflammatory factors and complement activation are associated in patients with type 2 diabetes, and (2) changes in hyperglycemia are related to changes in the concentration of the complement activation product, ASP.

Acute-Phase Proteins↗
PubMed2001

Leptin during assisted reproductive cycles: the effect of ovarian stimulation and of very early pregnancy.

Leptin may have a role in human reproduction. The impact of IVF and of very early pregnancy on serum leptin concentrations was studied in 66 infertile patients, of whom 19 became pregnant. Ovarian suppression was accompanied by a fall in leptin concentrations (21 +/- 4%, mean +/- SE; P < 0.01) from the mid-luteal phase, and ovarian stimulation by a rise (76 +/- 8%; P < 0.0001) from suppression. The mid-luteal concentration of leptin after stimulation was 28 +/- 7% higher than that during the preceding normal cycle (P < 0.001). Concentrations of leptin and oestradiol were related before treatment, at ovarian suppression and at 8 days after oocyte retrieval. In addition, the rises in leptin and oestradiol concentrations during stimulation were correlated, but only in those patients who became pregnant (r = 0.69; P = 0.001). Women with a successful pregnancy had higher concentrations of leptin (18.7 +/- 4.8 microg/l) at 12 days after embryo transfer than those who had miscarriages (10.0 +/- 1.9 microg/l; P < 0.001), or those failing to become pregnant (11.6 +/- 1.2 microg/l; P < 0.0001). We concluded that leptin concentrations are influenced by ovarian function and that the relationship between leptin and oestrogen (but not a single leptin concentration), may be an important factor for the outcome of IVF.

Adult↗
PubMed2001

Comparison between 1 year oral and transdermal oestradiol and sequential norethisterone acetate on circulating concentrations of leptin in postmenopausal women.

BACKGROUND: Oral and transdermal postmenopausal hormone replacement therapy (HRT) affects lipid and glucose metabolism differently, which is of significance in the release of leptin by adipocytes. Moreover, oestrogen and progesterone can stimulate leptin secretion in women of reproductive age. Therefore, we compared the effects of oral and transdermal oestrogen plus progestin regimen on plasma leptin in 38 healthy postmenopausal women with normal body mass index (BMI), who wished to use HRT to control incapacitating climacteric symptoms. METHODS: The women were randomized to treatment with oral HRT (2 mg oestradiol on days 1--12, 2 mg oestradiol plus 1 mg norethisterone acetate (NETA) on days 13--22, and 1 mg oestradiol on days 23--28, n = 19), or with transdermal HRT (50 microg/day of oestradiol on days 1--13, and 50 microg oestradiol plus 250 microg/day NETA on days 14--28, n = 19) for 1 year. Plasma samples were collected before and at oestradiol + NETA phase after 2, 6 and 12 months treatment and were assayed for leptin. RESULTS: The baseline leptin, ranging from 3.3 to 34.9 microg/l, was significantly associated with BMI (r = 0.78, P < 0.0001 ), but showed no difference between women in oral HRT (geometric mean 13.9 microg/l, 95% confidence interval (CI) 10.1--17.6 microg/l) or transdermal HRT group (geometric mean 12.0 microg/l, 95% CI 9.7--14.3 microg/l). Neither oral nor transdermal oestradiol + NETA caused any significant changes in plasma leptin (or BMI) after 2, 6, or 12 months of treatment. CONCLUSION: Leptin is an unsuitable factor to detect oestradiol + NETA-induced metabolic changes in postmenopausal women.

Administration, Cutaneous↗
PubMed2001

Postnatal changes in concentrations of free and bound leptin.

AIM: To evaluate the effect of maternal diabetes on the concentrations of free and bound leptin at birth and during postnatal adaptation. METHODS: Total, bound, and free leptin concentrations and the percentage of free leptin were measured in cord plasma and plasma at 3 days of age of 13 term infants of mothers with gestational diabetes mellitus (GDM) and 13 term infants of healthy mothers. Gestational age was 40.2 (1.4) weeks, and birth weight was 3693 (549) g (means (SD)). RESULTS: At birth, infants of mothers with GDM had significantly higher concentrations of total, bound, and free leptin and a higher percentage of free leptin (all p < 0.05). In all infants, these concentrations were significantly lower at 3 days of age than at birth (all p < 0.003), and the differences in concentrations of total, bound, and free leptin between the two groups were no longer significant. In infants of mothers with GDM, the percentage of free leptin remained unchanged, and was higher (p<0.05) than in infants of healthy mothers; in the latter group the percentage of free leptin significantly declined (p = 0.02). CONCLUSIONS: GDM appears to influence fetoplacental leptin metabolism. This effect may be mediated through altered maternal glucose metabolism, or insulinaemia, or both.

Anthropometry↗
PubMed2001

Plasma acylation stimulating protein concentration and subcutaneous adipose tissue C3 mRNA expression in nondiabetic and type 2 diabetic men.

We studied the effect of an oral fat load on plasma acylation stimulating protein (ASP) concentrations in 9 lean healthy (age 59+/-2 years, body mass index [BMI] 23.2+/-0.4 kg/m(2); both mean+/-SEM), 9 obese nondiabetic (58+/-2 years, BMI 29.4+/-0.5 kg/m(2)), and 12 type 2 diabetic (60+/-2 years, BMI 29.6+/-1.0 kg/m(2)) men. Because ASP is a cleavage product of complement protein C3 (C3adesArg) and its secretion is regulated by insulin, we also examined the subcutaneous adipose tissue expression of C3 mRNA before and after a 240-minute euglycemic hyperinsulinemic clamp in a subgroup of these men. Plasma ASP concentration and adipose tissue C3 mRNA expression were higher in the obese groups than in the lean men. Plasma ASP concentration did not change significantly after the fat load. Fasting plasma ASP concentration and C3 mRNA expression were correlated negatively with insulin sensitivity and positively with the magnitude of postprandial lipemia in nondiabetic but not in type 2 diabetic men. The expression of C3 mRNA was not regulated by insulin. These data suggest that ASP is associated with whole-body glucose and lipid metabolism in nondiabetic individuals, whereas metabolic disturbances in diabetes may overcome the regulatory role of ASP in lipid and glucose metabolism.

Adipose Tissue↗
PubMed2000

Antiestrogenic tamoxifen and toremifene increase serum leptin levels in postmenopausal breast cancer patients.

OBJECTIVES: Because estrogens stimulate the synthesis and release of leptin in the adipocytes, the effect of antiestrogens on the circulating leptin levels were studied. METHODS: Thirty postmenopausal patients with breast cancer were randomized to start either with tamoxifen (20 mg/day, n=15) or toremifene (40 mg/day, n=15), and the patients were examined and serum leptin concentrations measured before the study and at 6 and 12 months. RESULTS: The baseline leptin concentrations ranged from 4.4 to 60.0 microg/l (15.3+/-13.1 microg/l, mean+/-S.D.), and it correlated positively with the body mass index (BMI) of the subjects (r=0.73, P=0.0001). Taking as a whole the antiestrogen regimen was associated with elevated leptin levels at 6 months (19.5+/-13.8 microg/l, P=0.0001) but no excess increase in leptin levels were seen at 12 months (20.9+/-13.5 microg/l, NS). Subgroup analysis showed no difference between the effects of tamoxifen or toremifene on leptin. BMI increased in 21 women (from 26.2+/-4.3 to 27.3+/-4.8 kg/m2, P=0.0001) at 6 months, but not after that; in nine women BMI did not change. There was no significant correlation between the change in leptin levels and the change in BMI in either group implying that antiestrogens may specifically stimulate leptin production. CONCLUSIONS: Antiestrogens may stimulate the synthesis and release of leptin in the adipocytes. This effect of antiestrogens resembles the effect of estrogen and consequently stimulation of leptin production can be added to the estrogenic effects of antiestrogens.

Antineoplastic Agents, Hormonal↗
PubMed2000

Increased fetal leptin in type I diabetes mellitus pregnancies complicated by chronic hypoxia.

AIMS/HYPOTHESIS: The purpose of this study was to examine whether fetal leptin concentration correlates with severity of chronic or subchronic fetal hypoxia as indicated by increased fetal concentrations of erythropoietin in fetuses of mothers with Type I (insulin dependent) diabetes mellitus. METHODS: We measured leptin and erythropoietin concentrations in cord plasma and amniotic fluid with radioimmunoassay in 25 pregnancies (gestational age 37.2 +/- 1.0 weeks). Fetuses with amniotic fluid erythropoietin over 22.5 mU/ml were classified as hypoxic (n = 9) and those with amniotic fluid erythropoietin below 22.5 mU/ml (n = 16) as non-hypoxic. RESULTS: The hypoxic fetuses had significantly higher cord leptin concentrations than non-hypoxic fetuses (median 36.8; range, 12.5-135.1 vs median 16.2; range, 3.7-52.2 micrograms/l), (p = 0.0066). Cord plasma leptin (n = 25) correlated directly with amniotic fluid erythropoietin (r = 0.727, p = 0.0001), with cord plasma erythropoietin (r = 0.644, p = 0.0005) and with the maternal last trimester HbA1C (r = 0.612, p = 0.0019) and negatively with cord artery pO2 (r = -0.440, p = 0.032), and pH (r = -0.414, p = 0.040). CONCLUSION/INTERPRETATION: Fetal leptin concentrations increased concomitantly with erythropoietin during chronic or subchronic hypoxia. This phenomenon could indicate a role for leptin in fetal adaptation to hypoxia.

Amniotic Fluid↗
PubMed2000

Subcutaneous adipose tissue expression of tumour necrosis factor-alpha is not associated with whole body insulin resistance in obese nondiabetic or in type-2 diabetic subjects.

BACKGROUND: An association with subcutaneous adipose tissue TNFalpha expression and insulin resistance has been suggested in obesity/type-2 diabetes, but this has not been examined directly. In the first part of the study we investigated whether this association is present in 7 lean, 10 obese nondiabetic and 9 type-2 diabetic men. In the second part of the study we examined the relationship between adipose tissue TNFalpha mRNA levels and BMI in 81 nondiabetic subjects spanning a wide range of BMIs. METHODS: Subcutaneous adipose tissue TNFalpha mRNA levels and insulin sensitivity were determined with quantitative RT-competitive PCR and hyperinsulinaemic clamp, respectively. RESULTS: Subcutaneous adipose tissue TNFalpha mRNA levels were similar in 7 lean and 10 obese nondiabetic and 9 type-2 diabetic men (P = 0.68), and did not change in response to 240-min hyperinsulinaemia. TNFalpha mRNA levels and insulin sensitivity were not correlated. Unexpectedly, no correlation between TNFalpha mRNA and BMI was found. The relationship between adipose tissue TNFalpha mRNA and BMI was examined further in 31 male and 50 female nondiabetic subjects. The subcutaneous adipose tissue TNFalpha mRNA level correlated with BMI in all subjects (rS = 0.32, P < 0.01), and in a subgroup analysis in men (rS = 0.55, P < 0.01) but not in women (rS = - 0.08). The correlation in men was dependent on a fourfold higher TNFalpha mRNA level in 5 morbidly obese men while there was no difference in TNFalpha mRNA levels in lean or obese men. CONCLUSIONS: Subcutaneous adipose tissue TNFalpha expression does not correlate with insulin sensitivity in nondiabetic or type-2 diabetic men; is not regulated by acute hyperinsulinaemia; and is increased only in morbidly obese men.

Adipose Tissue↗
PubMed2000

No evidence for mutations of the leptin or leptin receptor genes in women with polycystic ovary syndrome.

Polycystic ovarian syndrome (PCOS) is often associated with obesity and insulin resistance, both of which are features that are linked to the leptin and leptin receptor (LEPR) genes. Analysis of the leptin gene by sequencing samples from 38 well-characterized patients with PCOS revealed no mutations of the coding exons. In single-stranded conformational polymorphism (SSCP) analysis and subsequent sequencing of the LEPR gene revealed previously identified amino acid variants in exons 2, 4 and 12 as well as the pentanucleotide insertion in the 3'-untranslated region (3'-UTR). The allele frequencies of these polymorphisms did not differ from those in the general population, as assessed in 122 female controls. Compared with non-carriers, serum insulin concentrations tended to be lower in the carriers of the variant LEPR exon 12 allele as well as in the carriers of the variant LEPR 3'-UTR allele, a marker previously suggested to be associated with serum insulin concentrations. In conclusion, PCOS is not commonly a consequence of mutations of the leptin or LEPR genes. However, our data support the hypothesis that variations in the LEPR gene locus have an effect on insulin regulation.

Adult↗
PubMed2000

Increased leptin concentration in preterm infants of pre-eclamptic mothers.

AIM: To study the effect of maternal pre-eclampsia on cord plasma leptin concentrations in preterm infants. METHODS: Leptin concentration was analysed in cord plasma of 74 preterm infants, gestational age 24 to 32 weeks. Of these, 14 were born to pre-eclamptic mothers, in 10 intrauterine growth retardation (IUGR) was present, and 59 had been exposed antenatally to corticosteroids. RESULTS: The mean (SD) concentration of cord plasma leptin was 1.31 (0.88) microg/l. A significant correlation was found between leptin concentration and gestational age (r = 0.336; p = 0.0037). Leptin levels were higher in infants of pre-eclamptic mothers (p = 0.0007), in those with IUGR (p = 0.0005), and in infants exposed antenatally to corticosteroids (p = 0.02). In multiple regression analysis, leptin was associated with gestational age and maternal pre-eclampsia (both p < 0.05), but not with antenatal corticosteroids. CONCLUSIONS: Increased fetal leptin in maternal pre-eclampsia may reflect a physiological adaptation to fetal stress such as hypoxia.

Birth Weight↗
PubMed2000

Fatty acid transport protein-1 mRNA expression in skeletal muscle and in adipose tissue in humans.

Fatty acid transporter protein (FATP)-1 mRNA expression was investigated in skeletal muscle and in subcutaneous abdominal adipose tissue of 17 healthy lean, 13 nondiabetic obese, and 16 obese type 2 diabetic subjects. In muscle, FATP-1 mRNA levels were higher in lean women than in lean men (2.2 +/- 0.1 vs. 0.6 +/- 0.2 amol/microg total RNA, P < 0.01). FATP-1 mRNA expression was decreased in skeletal muscle in obese women both in nondiabetic and in type 2 diabetic patients (P < 0.02 vs. lean women in both groups), and in all women there was a negative correlation with basal FATP-1 mRNA level and body mass index (r = -0.74, P < 0.02). In men, FATP-1 mRNA was expressed at similar levels in the three groups both in skeletal muscle (0.6 +/- 0.2, 0.6 +/- 0.2, and 0.8 +/- 0.2 amol/microg total RNA in lean, obese, and type 2 diabetic male subjects) and in adipose tissue (0.9 +/- 0.2 amol/microg total RNA in the 3 groups). Insulin infusion (3 h) reduced FATP-1 mRNA levels in muscle in lean women but not in lean men. Insulin did not affect FATP-1 mRNA expression in skeletal muscle in obese nondiabetic or in type 2 diabetic subjects nor in subcutaneous adipose tissue in any of the three groups. These data show a gender-related difference in the expression of the fatty acid transporter FATP-1 in skeletal muscle of lean individuals and suggest that changes in FATP-1 expression may not contribute to a large extent to the alterations in fatty acid uptake in obesity and/or type 2 diabetes.

Abdomen↗
PubMed1999

Troglitazone reduces hyperglycaemia and selectively acute-phase serum proteins in patients with Type II diabetes.

AIMS/HYPOTHESIS: Inflammation could play a part in insulin resistance. Thiazolidinediones, new antidiabetic drugs, possess anti-inflammatory effects in vitro. We investigated if acute-phase serum proteins are increased in patients with Type II (non-insulin-dependent) diabetes mellitus who had been treated with insulin and whether troglitazone has anti-inflammatory effects in vivo. METHODS: A total of 27 patients (age 63.0+/-1.7 years, HbA1c 8.8+/-0.3%, BMI 32.7+/-0.8 kg/m2, duration 15.2+/-1.4 years, insulin dose 73.3+/-7.0 U/day) participated in the study. The patients received daily either 400 mg troglitazone or placebo for 16 weeks. Blood samples were taken at baseline, at the end of therapy and after a follow-up time of 23+/-4 days. RESULTS: The concentrations of serum amyloid A (6.2+/-1.1 mg/l) and C-reactive protein (6.1+/-1.1 mg/l) were increased (p < 0.001) and complement protein C3 (1.69+/-0.05 g/l) was also above the reference range for healthy subjects. Placebo treatment had no effect on glucose or inflammation, whereas troglitazone reduced fasting glucose (from 10.4+/-0.6 mmol/l to 8.1+/-0.5 mmol/l, p < 0.01), HbA1c (from 8.7+/-0.3% to 7.5+/-0.3%, p < 0.01), insulin requirements (from 75+/-10 U/day to 63+/-10 U/day, p < 0.05), serum amyloid A (from 6.3+/-1.5 mg/l to 4.0+/-1.3 mg/l, p = 0.001), alpha-1-acid glycoprotein (from 906+/-51 mg/l to 729+/-52 mg/l, p = 0.001) and C3 (from 1.72+/-0.07 g/l to 1.66+/-0.06 g/l, p < 0.05) but not alpha-1-antitrypsin, ceruloplasmin, C-reactive protein or haptoglobin significantly. Concentrations of glucose and acute-phase reactants had returned to those before treatment at the follow-up visit. CONCLUSION/INTERPRETATION: In Type II diabetic patients serum amyloid A and complement protein C3 are raised. Troglitazone exerts a selective reversible action on some acute-phase proteins and C3 but not on others in conjunction with the improvement in glucose metabolism.

Acute-Phase Proteins↗
PubMed1999

Changes in leptin concentration during the early postnatal period: adjustment to extrauterine life?

There are substantial alterations in fuel homeostasis immediately after birth. Leptin is a putative regulator of energy metabolism. Consequently, the aim of this study was to examine whether there are changes in circulating leptin concentrations during the early postnatal period. Umbilical cord mixed blood samples were taken at delivery, and a venous blood sample was obtained at 3 d of age from 38 healthy newborn infants (20 male, 18 female; gestational age 36.3 to 41.9 wk) for analysis of leptin concentration with radioimmunoassay. Cord plasma leptin concentration was 9.7+/-5.2 microg/L (mean+/-SD), with no gender difference between male (8.6+/-4.6 microg/L) and female (10.9+/-5.6 microg/L) infants. In male newborns, cord plasma leptin concentration correlated with arm circumference (r = 0.48, p < 0.05), and in female newborns with body mass index (r = 0.62, p < 0.01), thickness of the s.c. fat (r = 0.54, p < 0.05), and arm circumference (r = 0.72, p < 0.01). By the third postnatal day, plasma leptin decreased similarly in male (to 1.8+/-0.4 microg/L, p < 0.001) and female (to 2.3+/-0.8 microg/L, p < 0.001) infants, when there was a significant gender difference in leptin levels (p = 0.01). At 3 d of age, plasma leptin correlated with weight (r = 0.49, p < 0.05) and arm circumference (r = 0.49, p < 0.05) in female but not in male newborns. In conclusion, 1) circulating leptin already correlates with adiposity at birth in female but not in male newborn infants and 2) leptin decreases markedly in both genders by the third postnatal day, and the gender difference with higher leptin levels in females develops by that time. Thus, the postnatal decrease in plasma leptin concentration may be a physiologically feasible adaptation to profound alterations in fuel homeostasis during the first days of extrauterine life.

Adipose Tissue↗
PubMed1998

Insulin-independent glucose transport regulates insulin sensitivity.

The glucose transport proteins (GLUT1 and GLUT4) facilitate glucose transport into insulin-sensitive cells. GLUT1 is insulin-independent and is widely distributed in different tissues. GLUT4 is insulin-dependent and is responsible for the majority of glucose transport into muscle and adipose cells in anabolic conditions. We suggest the hypothesis that insulin resistance is dependent on whether glucose is entering through GLUT1 or GLUT4 and on the two functional compartments of glucose 6-phosphate formation within the cell. Glucose entering the muscle cell through GLUT4 and phosphorylated by hexokinase II is mainly directed to glycogen synthesis and glycolysis. If glucose is entering through GLUT1 and phosphorylated by hexokinase I, the glucose 6-phosphate so formed is available for all metabolic pathways, including the hexosamine pathway. Hexosamines have a negative feedback effect on GLUT4, and reduced GLUT4 activity decreases insulin-mediated glucose uptake. Thus, insulin-independent glucose transport through GLUT1 can meet the basal needs of the muscle cell. If glucose entrance through GLUT1 and the activation of the hexosamine pathway is abundant, it can decrease the insulin-mediated glucose transport through GLUT4 leading to insulin resistance.

Animals↗