The prevalence and distribution of the amyloidogenic transthyretin (TTR) V122I allele in Africa.

BACKGROUND: Transthyretin (TTR) pV142I (rs76992529-A) is one of the 113 variants in the human TTR gene associated with systemic amyloidosis. It results from a G to A transition at a CG dinucleotide in the codon for amino acid 122 of the mature protein (TTR V122I). The allele frequency is 0.0173 in African Americans. METHODS: PCR-based assays to genotype 2767 DNA samples obtained from participants in genetic studies from various African populations supplemented with sequencing data from 529 samples within the 1000 Genomes Project. RESULTS: The rs76992529-A variant allele was most prevalent (allele frequency 0.0253) in the contiguous West African countries of Sierra Leone, Guinea, Ivory Coast, Burkina Faso, Ghana, and Nigeria. In other African countries, the mean allele frequency was 0.011. CONCLUSIONS: Our data are consistent with a small number of founder carriers of the amyloidogenic TTR V122I (p.Val142Ile) allele in southern West Africa, with no apparent advantage or disadvantage of an allele carrying newborn reaching adulthood. In U.S. African Americans, the allele represents a significant risk for congestive heart failure late in life. If clinical penetrance is similar in African countries with high allele frequencies, then cardiac amyloidosis could also represent a significant cause of heart disease in the elderly in those populations.

Weight maintenance: challenges, tools and strategies for primary care physicians.

Obesity is recognized as a chronic disease and one of the major healthcare challenges facing us today. Weight loss can be achieved via lifestyle, pharmacological and surgical interventions, but weight maintenance remains a lifetime challenge for individuals with obesity. Guidelines for the management of obesity have highlighted the role of primary care providers (PCPs). This review examines the long-term outcomes of clinical trials to identify effective weight maintenance strategies that can be utilized by PCPs. Because of the broad nature of the topic, a structured PubMed search was conducted to identify relevant research articles, peer-reviewed reviews, guidelines and articles published by regulatory bodies. Trials have demonstrated the benefit of sustained weight loss in managing obesity and its comorbidities. Maintaining 5-10% weight loss for ≥1 year is known to ameliorate many comorbidities. Weight maintenance with lifestyle modification - although challenging - is possible but requires long-term support to reinforce diet, physical activity and behavioural changes. The addition of pharmacotherapy to lifestyle interventions promotes greater and more sustained weight loss. Clinical evidence and recently approved pharmacotherapy has given PCPs improved strategies to support their patients with maintenance of weight loss. Further studies are needed to assess the translation of these strategies into clinical practice.

Carboxylated and uncarboxylated forms of osteocalcin directly modulate the glucose transport system and inflammation in adipocytes.

Osteocalcin is secreted by osteoblasts and improves insulin sensitivity in vivo, although mechanisms remain unclear. We tested the hypothesis that osteocalcin directly modulates cell biology in insulin-targeted peripheral tissues. In L-6 myocytes, osteocalcin stimulated glucose transport both in the absence (basal) and presence of insulin. Similarly, in primary cultured adipocytes, both carboxylated and uncarboxylated osteocalcin increased basal and insulin-stimulated glucose transport as well as insulin sensitivity. Osteocalcin also increased basal and insulin-stimulated glucose oxidation, though there was no effect on fatty acid synthesis or lipolysis. In primary-cultured adipocytes, both forms of osteocalcin suppressed secretion of tumor necrosis factor alpha into the media; however, only carboxylated osteocalcin suppressed interleukin 6 release, and neither form of osteocalcin modulated monocyte chemoattractant protein-1 secretion. Both carboxylated and uncarboxylated osteocalcin increased secretion of adiponectin and the anti-inflammatory cytokine interleukin 10. In conclusion, both carboxylated and uncarboxylated osteocalcin directly increase glucose transport in adipocytes and muscle cells, while suppressing proinflammatory cytokine secretion and stimulating interleukin 10 and adiponectin release. Thus, these results provide a mechanism for the insulin-sensitizing effects of osteocalcin and help elucidate the role that bone plays in regulating systemic metabolism.

AdR1-TG/TALLYHO mice have improved lipid accumulation and insulin sensitivity.

BACKGROUND: Overexpression of adiponectin receptor 1 in macrophages can physiologically modulate metabolic activities in vivo by enhancing adiponectin actions in distal metabolically active tissues. To investigate the effects of enhanced adiponectin actions in TALLYHO (TH) diabetic mouse model, we crossed the adiponectin receptor 1 macrophage-specific transgenic mice (AdR1-TG) with the TALLYHO diabetic mice (TH) to examine the changes of lipid accumulation and insulin sensitivity in these mice. METHODS: AdR1-TG/TH and the control WT/TH mice were fed either normal diet or high fat diet for 28weeks. Whole body weights of these mice were measured and mouse sera were analyzed for the levels of cholesterol, triglyceride, and free fatty acids. Glucose tolerance testing (GTT) and insulin tolerance testing (ITT) in these mice were performed to investigate systemic insulin sensitivity in vivo. Molecular markers for insulin signaling pathway in mouse skeletal muscle tissues, IRS-1 and AKT, were examined. Mouse serum insulin levels were measured and Sirt1 gene expression in mouse pancreatic tissues was also quantified related to the insulin secretion. The Caspase 3 protein levels were analyzed by Western blot methods. RESULTS: Compared to the control WT/TH mice, AdR1-TG/TH mice showed significantly lower body weights under either normal diet or high fat diet and the mouse serum levels of cholesterol, triglyceride and free fatty acids were significantly decreased in the transgenic crossed mice when compared to those from the control mice. Improved GTT and ITT tests indicating increased systemic insulin sensitivity in the transgenic crossed mice demonstrated the enhanced adiponectin actions on the systemic metabolism in vivo. The increases of insulin secretion and its related gene expression were also detected in the transgenic crossed mice. In contrast, the control mice showed hypertrophy pancreases companying with high apoptosis gene expression. These results suggest that enhanced adiponectin actions by overexpressing adiponectin receptor 1 in macrophages can provide unique interactions with the metabolic tissues/cells, improving lipid accumulation and insulin sensitivity in TALLYHO diabetic mice.

Prostaglandin A2 enhances cellular insulin sensitivity via a mechanism that involves the orphan nuclear receptor NR4A3.

We have previously reported that members of the NR4A family of orphan nuclear receptors can augment insulin's ability to stimulate glucose transport in adipocytes. In the current study, we endeavored to test for an insulin-sensitizing effect in muscle cells and to identify a potential transactivator. Lentiviral constructs were used to engineer both hyperexpression and shRNA silencing of NR4A3 in C2C12 myocytes. The NR4A3 hyper-expression construct led to a significant increase in glucose transport rates in the presence of maximal insulin while the NR4A3 knock-down exhibited a significant reduction in insulin-stimulated glucose transport rates. Consistently, insulin-mediated AKT phosphorylation was increased by NR4A3 hyperexpression and decreased following shRNA NR4A3 suppression. Then, we examined effects of prostaglandin A2 (PGA2) on insulin action and NR4A3 transactivation. PGA2 augmented insulin-stimulated glucose uptake in C2C12 myocytes and AKT phosphorylation after 12-h treatment, without significant effects on basal transport or basal AKT phosphorylation. More importantly, we demonstrated that PGA2 led to a greater improvement in insulin-stimulated glucose rates in NR4A3 overexpressing C2C12 myocytes, when compared with Lac-Z controls stimulated with insulin and PGA2. Moreover, the sensitizing effect of PGA2 was significantly diminished in NR4A3 knockdown myocytes compared to scramble controls. These results show for the first time that: (i) PGA2 augments insulin action in myocytes as manifested by enhanced stimulation of glucose transport and AKT phosphorylation; and (ii) the insulin sensitizing effect is dependent upon the orphan nuclear receptor NR4A3.

Noggin is novel inducer of mesenchymal stem cell adipogenesis: implications for bone health and obesity.

Noggin is a glycosylated-secreted protein known so far for its inhibitory effects on bone morphogenetic protein (BMP) signaling by sequestering the BMP ligand. We report here for the first time a novel mechanism by which noggin directly induces adipogenesis of mesenchymal stem cells independently of major human adipogenic signals through C/EBPδ, C/EBPα and peroxisome proliferator-activated receptor-γ. Evaluation of a possible mechanism for noggin-induced adipogenesis of mesenchymal stem cells identified the role of Pax-1 in mediating such differentiation. The relevance of elevated noggin levels in obesity was confirmed in a preclinical, immunocompetent mouse model of spontaneous obesity and in human patients with higher body mass index. These data clearly provide a novel role for noggin in inducing adipogenesis and possibly obesity and further indicates the potential of noggin as a therapeutic target to control obesity.

Effects of colesevelam on glucose absorption and hepatic/peripheral insulin sensitivity in patients with type 2 diabetes mellitus.

AIM: Colesevelam lowers glucose and low-density lipoprotein cholesterol levels in patients with type 2 diabetes mellitus. This study examined the mechanisms by which colesevelam might affect glucose control. METHODS: In this 12-week, randomized, double-blind, placebo-controlled study, subjects with type 2 diabetes and haemoglobin A(1c) (HbA(1c)) ≥7.5% on either stable diet and exercise or sulphonylurea therapy were randomized to colesevelam 3.75 g/day (n = 16) or placebo (n = 14). Hepatic/peripheral insulin sensitivity was evaluated at baseline and at week 12 by infusion of (3) H-labelled glucose followed by a 2-step hyperinsulinemic-euglycemic clamp. Two 75-g oral glucose tolerance tests (OGTTs) were conducted at baseline, one with and one without co-administration of colesevelam. A final OGTT was conducted at week 12. HbA(1c) and fasting plasma glucose (FPG) levels were evaluated pre- and post-treatment. RESULTS: Treatment with colesevelam, compared to placebo, had no significant effects on basal endogenous glucose output, response to insulin or on maximal steady-state glucose disposal rate. At baseline, co-administration of colesevelam with oral glucose reduced total area under the glucose curve (AUC(g)) but not incremental AUC(g). At week 12, neither total AUC(g) nor incremental AUC(g) were changed from pre-treatment values in either group. Post-load insulin levels increased with colesevelam at 30 and 120 min, but these changes in total area under the insulin curve (AUC(i)) and incremental AUC(i) did not differ between groups. Both HbA(1c) and FPG improved with colesevelam, but treatment differences were not significant. CONCLUSIONS: Colesevelam does not affect hepatic or peripheral insulin sensitivity and does not directly affect glucose absorption.

Nuclear magnetic resonance-determined lipoprotein subclass profile in the DCCT/EDIC cohort: associations with carotid intima-media thickness.

AIMS: To relate nuclear magnetic resonance lipoprotein subclass profiles (NMR-LSP) and other lipoprotein-related factors with carotid intima-media thickness (IMT) in Type 1 diabetes. METHODS: Lipoprotein-related factors were determined in sera (obtained in 1997-1999) from 428 female [age 39 +/- 7 years (mean +/- SD)] and 540 male (age 40 +/- 7 years) Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) participants. NMR quantifies chylomicrons, three very low-density lipoprotein (VLDL) subclasses, intermediate density lipoprotein (IDL), three low-density lipoprotein (LDL) subclasses, two high-density lipoprotein (HDL) subclasses, mean VLDL, LDL and HDL size, and LDL particle concentration. Conventional lipids, ApoA1, ApoB and Lp(a) and in vitro LDL oxidizibility were also measured. IMT was determined (in 1994-1995) using high-resolution B-mode ultrasound. Relationships between IMT and lipoproteins were analysed by multiple linear regression, controlling for age, diabetes-related factors, and cardiovascular disease (CVD) risk factors. RESULTS: IMT associations with lipoproteins were stronger for the internal than the common carotid artery, predominantly involving LDL. Internal carotid IMT was positively (P < 0.05) associated with NMR-based LDL subclasses and particle concentration, and with conventional LDL-cholesterol and ApoB in both genders. Common carotid IMT was associated, in men only, with large VLDL, IDL, conventional LDL cholesterol and ApoB. CONCLUSIONS: NMR-LSP reveals significant associations with carotid IMT in Type 1 diabetic patients, even 4 years after IMT measurement. NMR-LSP may aid early identification of high-risk diabetic patients and facilitate monitoring of interventions. Longer DCCT/EDIC cohort follow-up will yield CVD events and IMT progression, permitting more accurate assessment of pre-morbid lipoprotein profiles as determinants of cardiovascular risk in Type 1 diabetes.

Adipocytes exhibit abnormal subcellular distribution and translocation of vesicles containing glucose transporter 4 and insulin-regulated aminopeptidase in type 2 diabetes mellitus: implications regarding defects in vesicle trafficking.

Insulin resistance in type 2 diabetes is due to impaired stimulation of the glucose transport system in muscle and fat. Different defects are operative in these two target tissues because glucose transporter 4 (GLUT 4) expression is normal in muscle but markedly reduced in fat. In muscle, GLUT 4 is redistributed to a dense membrane compartment, and insulin-mediated translocation to plasma membrane (PM) is impaired. Whether similar trafficking defects are operative in human fat is unknown. Therefore, we studied subcellular localization of GLUT4 and insulin-regulated aminopeptidase (IRAP; also referred to as vp165 or gp160), which is a constituent of GLUT4 vesicles and also translocates to PM in response to insulin. Subcutaneous fat was obtained from eight normoglycemic control subjects (body mass index, 29 +/- 2 kg/m2) and eight type 2 diabetic patients (body mass index, 30 +/- 1 kg/m2; fasting glucose, 14 +/- 1 mM). In adipocytes isolated from diabetics, the basal 3-O-methylglucose transport rate was decreased by 50% compared with controls (7.1 +/- 2.9 vs. 14.1 +/- 3.7 mmol/mm2 surface area/min), and there was no increase in response to maximal insulin (7.9 +/- 2.7 vs. 44.5 +/- 9.2 in controls). In membrane subfractions from controls, insulin led to a marked increase of IRAP in the PM from 0.103 +/- 0.04 to 1.00 +/- 0.33 relative units/mg protein, concomitant with an 18% decrease in low-density microsomes and no change in high-density microsomes (HDM). In type 2 diabetes, IRAP overall expression in adipocytes was similar to that in controls; however, two abnormalities were observed. First, in basal cells, IRAP was redistributed away from low-density microsomes, and more IRAP was recovered in HDM (1.2-fold) and PM (4.4-fold) from diabetics compared with controls. Second, IRAP recruitment to PM by maximal insulin was markedly impaired. GLUT4 was depleted in all membrane subfractions (43-67%) in diabetes, and there was no increase in PM GLUT4 in response to insulin. Type 2 diabetes did not affect the fractionation of marker enzymes. We conclude that in human adipocytes: 1) IRAP is expressed and translocates to PM in response to insulin; 2) GLUT4 depletion involves all membrane subfractions in type 2 diabetes, although cellular levels of IRAP are normal; and 3) in type 2 diabetes, IRAP accumulates in membrane vesicles cofractionating with HDM and PM under basal conditions, and insulin-mediated recruitment to PM is impaired. Therefore, in type 2 diabetes, adipocytes express defects in trafficking of GLUT4/IRAP-containing vesicles similar to those causing insulin resistance in skeletal muscle.

A role for the Agouti-Related Protein promoter in obesity and type 2 diabetes.

The murine Agouti-Related Protein (mAGRP) is upregulated in obese and diabetic mice and can stimulate hyperphagia when overexpressed in transgenic models. Here we report upstream nucleotide sequences of the human hAGRP gene with putative recognition sites for transcription factors including a site for the STAT transactivators. A polymorphism (-38C-->T) was identified in the promoter region and the C/C genotype had significantly higher promoter activity and affinity for transcription factors as tested in periphery- and hypothalamus-derived cell lines. The polymorphic site could affect the expression levels of hAGRP and the high expressing C/C genotype was significantly associated with high BMI and type 2 diabetes in Africans.

Ancestral proportions and admixture dynamics in geographically defined African Americans living in South Carolina.

We analyzed admixture in samples of six different African-American populations from South Carolina: Gullah-speaking Sea Islanders in coastal South Carolina, residents of four counties in the "Low Country" (Berkeley, Charleston, Colleton, and Dorchester), and persons living in the city of Columbia, located in central South Carolina. We used a battery of highly informative autosomal, mtDNA, and Y-chromosome markers. Two of the autosomal markers (FY and AT3) are linked and lie 22 cM apart on chromosome 1. The results of this study indicate, in accordance with previous historical, cultural, and anthropological evidence, a very low level of European admixture in the Gullah Sea Islanders (m = 3.5 +/- 0.9%). The proportion of European admixture is higher in the Low Country (m ranging between 9. 9 +/- 1.8% and 14.0 +/- 1.9%), and is highest in Columbia (m = 17.7 +/- 3.1%). A sex-biased European gene flow and a small Native American contribution to the African-American gene pool are also evident in these data. We studied the pattern of pairwise allelic associations between the FY locus and the nine other autosomal markers in our samples. In the combined sample from the Low Country (N = 548), a high level of linkage disequilibrium was observed between the linked markers, FY and AT3. Additionally, significant associations were also detected between FY and 4 of the 8 unlinked markers, suggesting the existence of significant genetic structure in this population. A continuous gene flow model of admixture could explain the observed pattern of genetic structure. A test conditioning on the overall admixture of each individual showed association of ancestry between the two linked markers (FY and AT3), but not between any of the unlinked markers, as theory predicts. Thus, even in the presence of genetic structure due to continuous gene flow or some other factor, it is possible to differentiate associations due to linkage from spurious associations due to genetic structure.

Reduced plasma leptin concentrations in bulimia nervosa.

Leptin is a protein produced by the ob-ob gene which inhibits food intake. Plasma levels have previously been reported to be altered in obesity and anorexia nervosa (AN) but not bulimia nervosa (BN). We measured fasting plasma leptin levels by radioimmunoassay in 53 subjects carefully studied at NIMH, including 37 women meeting DSM-III-R criteria for BN [10 with concurrent AN (body mass index (BMI)=14.1+/-1.4), 27 without AN (BMI=20.4+/-1.6)] and 16 normal control women (NCs) (BMI=21.1+/-2.0). Patients were medication-free and abstinent from bingeing and purging for three to four weeks prior to study. Plasma leptin levels were significantly correlated to BMI (r=0.41, P<0.002), weight (kg, r=0.43, P<0.001), and percent average body weight (%ABW, r=0.45, P<0.001) in the total group. Plasma leptin levels were lower in the BN subjects (3.4+/-2.5 ng/ml) compared to the NCs (6.1+/-2.6 ng/ml, P<0.001, ANCOVA) even after controlling for BMI and weight. There was no significant difference between BN subjects with AN (n=10, 2.6+/-2.6 ng/ml) and those without AN (n=27, 3.8+/-2.4 ng/ml), despite lower BMI in BN with AN. Furthermore, leptin levels were decreased in BN without AN compared with healthy controls, even though BMI was comparable in these two subgroups. Plasma leptin concentrations were negatively correlated with baseline plasma cortisol levels (n=49, r=-0.49, P<0.001) and positively correlated with prolactin responses following L-tryptophan (n=49, r=0.37, P<0.009) and m-chlorophenylpiperazine (n=52, r=0.24, P<0.09). This is the first known report of decreased plasma leptin levels in BN. The decrement in leptin concentration is not related to BMI, body weight, or the presence or absence of BN. HPA axis activation as well as serotonin dysregulation may be related to decreased leptin levels, which may in turn contribute to disinhibited eating in BN. Although current leptin levels were not correlated with self-reported previous binge frequency, the role of leptin in the pathophysiology of BN deserves further study.

Short-term impact of a church-based approach to lifestyle change on cardiovascular risk in African Americans.

While lifestyle modification decreases cardiovascular risk, there are barriers to lifestyle education in usual clinical practice, especially among the medically underserved. To address this gap, "Lighten Up," a church-based lifestyle program was developed in collaboration with the local African-American Christian community. Lighten Up includes a baseline health assessment (week 1), eight educational sessions (weeks 2-9) combining study of scripture and a health message, a short-term health check (week 10) and a long-term health check (week 52). Baseline and 10 week risk factor data have been obtained in 133 African Americans from eight sites (83% women) and form the basis of this report. At baseline, 76% of participants had two or more modifiable risk factors (overweight, hypertension, borderline high cholesterol, or diabetes). The entire group had significant short-term reductions in weight (-2.3 pounds, P<.01), mean blood pressure (BP, -2.1 mm Hg, P<.05), and triglycerides (-11 mg/dl, P<.05). Risk factor improvement was greater among the 60 subjects who attended 75% or more of the educational sessions. In this group, weight fell 2.9+/-0.6 pounds (mean +/- SEM; P<.01), mean BP declined 3.8+/-1.2 mm Hg (P<.01), total cholesterol was lowered 6+/-4 mg/ dl (P = .12), and triglycerides were reduced 17+/-9 mg/dl (P = .05). Lighten Up is reaching a group with multiple cardiovascular risk factors that is not optimally managed by existing healthcare resources. Of the 133 participants, 70% attended half or more of the sessions, and several components of the risk factor cluster were favorably affected.

Dual energy X-ray absorptiometry assessment of fat mass distribution and its association with the insulin resistance syndrome.

OBJECTIVE: To determine which dual energy X-ray absorptiometry (DXA)-derived indices of fat mass distribution are the most informative to predict the various parameters of the metabolic syndrome. RESEARCH DESIGN AND METHODS: A total of 87 healthy men, 63 lean (% fat < or =26) and 24 obese (% fat >26), underwent DXA scanning to evaluate body composition with respect to the whole body and the trunk, leg, and abdominal regions from L1 to L4 and from L3 to L4. These regions were correlated with insulin sensitivity determined by the euglycemic-hyperinsulinemic clamp, insulin area under the curve after oral glucose tolerance test (AUC I); triglyceride; total, HDL, and LDL cholesterol; free fatty acids; and blood pressure. The analyses were performed in all subjects, as well as in lean and obese groups separately. RESULTS: Among the various indices of body fat, DXA-determined adiposity in the abdominal cut at L1-4 level was the most predictive of the metabolic variables, showing significant relationships with glucose infusion rate ([GIR], mg kg(-1) lean body mass x min(-1)), triglyceride, and cholesterol, independent of total-body mass (r = -0.267, P<0.05; r = 0.316, P<0.005; and r = 0.319, P<0.005, respectively). Upon subanalysis, these correlations remained significant in lean men, whereas in obese men, only BMI and the amount of leg fat (negative relationship) showed significant correlations with triglyceride and cholesterol (r = 0.438, P<0.05; r = 0.458, P<0.05; r = -0.439, P<0.05; and r = -0.414, P<0.05, respectively). The results of a multiple regression analysis revealed that 47% of the variance in GIR among all study subjects was predicted by AUC I, fat L1-4, diastolic blood pressure (dBP), HDL, and triglyceride as independent variables. In the lean group, fat L1-4 alone accounted for 33% of the variance of GIR, whereas in obese men, AUC I and dBP explained 68% of the variance in GIR. CONCLUSIONS: The DXA technique applied for the evaluation of fat distribution can provide useful information regarding various aspects of the insulin resistance syndrome in healthy subjects. DXA can be a valid, accurate, relatively inexpensive, and safer alternative compared with other methods to investigate the role of abdominal body fat distribution on cardiovascular risk factors.

Mechanism of hexosamine-induced insulin resistance in transgenic mice overexpressing glutamine:fructose-6-phosphate amidotransferase: decreased glucose transporter GLUT4 translocation and reversal by treatment with thiazolidinedione.

Hexosamines have been hypothesized to mediate aspects of glucose sensing and toxic effects of hyperglycemia. For example, insulin resistance results when the rate-limiting enzyme for hexosamine synthesis, glutamine:fructose-6-phosphate amidotransferase (GFA), is overexpressed in muscle and adipose tissue of transgenic mice. The glucose infusion rates required to maintain euglycemia at insulin infusion rates of 0.5, 2, 15, and 20 mU/kg x min were 39-90% lower in such transgenic mice, compared with their control littermates (P < or = 0.01). No differences were observed in hepatic glucose output, serum insulin levels, or muscle ATP levels. Uptake of 2-deoxyglucose, measured under conditions of hyperinsulinemia, was significantly lower in transgenic hindlimb muscle, compared with controls (85.9 +/- 17.8 vs. 166.8 +/- 15.1 pmol deoxyglucose/g x min). The decrease in glucose uptake by transgenic muscle was associated with a disruption in the translocation of the insulin-stimulated glucose transporter GLUT4. Fractionation of muscle membranes on a discontinuous sucrose gradient revealed that insulin stimulation of control muscle led to a 28.8% increase in GLUT4 content in the 25% fraction and a 61.2% decrease in the 35% fraction. In transgenic muscle, the insulin-stimulated shifts in GLUT4 distribution were inhibited by over 70%. Treatment of the transgenic animals with the thiazolidinedione troglitazone completely reversed the defect in glucose disposal without changing GFA activity or the levels of uridine 5'-diphosphate-N-acetylglucosamine. Overexpression of GFA in skeletal muscle thus leads to defects in glucose transport similar to those seen in type 2 diabetes. These data support the hypothesis that excess glucose metabolism through the hexosamine pathway may be responsible for the diminished insulin sensitivity and defective glucose uptake that are seen with hyperglycemia.

Endogenous mutations in human uncoupling protein 3 alter its functional properties.

Human uncoupling protein (UCP3) is a mitochondrial transmembrane carrier that uncouples oxidative phosphorylation and is a candidate gene for obesity. Expression of native human UCP3 mutations in yeast showed complete loss (R70W), significant reduction (R143X), or no effect (V102I and IVS6+1G > A) on the uncoupling activity of UCP3. It is concluded that certain mutations in UCP3 alter its functional impact on membrane potential (deltaphi), possibly conferring susceptibility to develop metabolic diseases.

Expression of mRNAs encoding uncoupling proteins in human skeletal muscle: effects of obesity and diabetes.

To explore the potential role of the uncoupling protein (UCP) family in human obesity and diabetes, we have used the reverse transcription-polymerase chain reaction to quantify UCP mRNA expression in human skeletal muscle. Levels of mRNA for UCP2, and for both short (UCP3S) and long (UCP3L) forms of UCP3, were highly correlated in individuals, indicating that gene transcription of these UCPs may be coordinately regulated by common mechanisms. In normal glucose-tolerant individuals, muscle UCP2 mRNA levels were positively correlated with percentage of body fat and with BMI (r = 0.6 and P < 0.05 for both). UCP3S mRNA levels were also positively correlated with percentage of body fat (r = 0.52, P < 0.05), and UCP3L mRNA tended to increase as a function of obesity (0.05 < P < 0.1). UCP mRNA levels, however, were not correlated with resting metabolic rate. UCP3S and UCP3L mRNA levels (P < 0.05) and the UCP2 mRNA level (P = 0.09) were increased by 1.8- to 2.7-fold in type 2 diabetes, an effect that could not be explained by obesity. No significant difference was found for UCP2, UCP3S, or UCP3L mRNA levels between insulin-sensitive and insulin-resistant nondiabetic subgroups. We conclude that 1) skeletal muscle mRNA levels encoding UCP2 and UCP3 are correlated among individuals and may be coordinately regulated; 2) UCP3 expression is not regulated by differential effects on UCP3L and UCP3S forms of the mRNA; and 3) UCP mRNA expression tends to increase in muscle as a function of obesity but not of resting metabolic rate or insulin resistance, and is increased in patients with type 2 diabetes.

Diabetes research in South Carolina: past, present, and future.

Medical investigators in South Carolina have been on the "cutting edge" of diabetes research for a number of decades. Despite this fact, our state ranks second in the nation in diabetes prevalence, and diabetes complications are more severe here than anywhere else. It is from the efforts of these investigators that our hope for a brighter future comes. Through a concerted effort toward prevention, improvements in care, and investigation of the pathophysiology of diabetes and its complications, researchers may reduce the substantial burden of diabetes in our state and throughout the world.