Assessment of hepatic sensitivity to glucagon in NIDDM: use as a tool to estimate the contribution of the indirect pathway to nocturnal glycogen synthesis

NIDDM is associated with excessive rates of endogenous glucose production in both the postabsorptive and postprandial states. To determine whether this is due to an intrinsic increase in hepatic sensitivity to glucagon, 9 NIDDM and 10 nondiabetic subjects were studied on three occasions. On each occasion, glycogen was labeled the evening before the study with subjects ingesting meals containing [6-3H]galactose. Beginning at 6:00 A.M. on the following morning, somatostatin was infused to inhibit endogenous hormone secretion. Insulin concentrations were maintained constant at basal levels (defined as that necessary to keep glucose at approximately 5 mmol/l) in each individual. On one occasion, glucagon was infused at a rate of 0.65 ng x kg(-1) x min(-1) throughout the experiment, resulting in glucagon concentrations of approximately 130 pg/ml and a slow but comparable fall in endogenous glucose production with time in both groups. On the other two occasions, the glucagon infusion was increased at 10:00 A.M. to either 1.5 or 3.0 ng x kg(-1) x min(-1), resulting in an increase in glucagon concentrations to approximately 180 and 310 pg/ml, respectively. The increment in endogenous glucose production (i.e., area above basal) did not differ in diabetic and nondiabetic subjects during either the 1.5 ng x kg(-1) x min(-1) (0.75 +/- 0.055 vs. 0.78 +/- 0.048 mmol/kg) or 3.0 ng x kg(-1) x min(-1) (1.06 +/- 0.066 vs. 1.10 +/- 0.073 mmol/kg) glucagon infusions. In contrast, the amount of [6-3H]glucose released from glycogen was lower (P < 0.05) in the diabetic than nondiabetic subjects during both glucagon infusions. The specific activity of glycogen, calculated as the integrated release of [6-3H]glucose divided by the integrated release of unlabeled glucose, was lower (P < 0.05) in diabetic subjects than in nondiabetic subjects during both the 1.5 ng x kg(-1) x min(-1) (19.0 +/- 3.9 vs. 41.4 +/- 5.7 dpm/micromol) and 3.0 ng x kg(-1) x min(-1) (19.1 +/- 3.1 vs. 36.5 +/- 7.2 dpm/micromol) glucagon infusions, implying that a greater portion of the glucose released from glycogen was derived from the indirect pathway. We concluded that although NIDDM is not associated with an intrinsic alteration in hepatic sensitivity to glucagon, it does alter the relative contributions of the direct and indirect pathways to nocturnal glycogen synthesis.

Unique organization of the CTX genetic element in Vibrio cholerae O139 strains which reemerged in Calcutta, India, in September 1996

We studied the restriction fragment length polymorphism of the rRNA gene and CTX genetic element in Vibrio cholerae O139 Bengal, which resurged in Calcutta in September 1996 after a gap of 32 months. While the strains from this resurgence were indistinguishable from the earlier strains by ribotyping, the structure of the CTX genetic element present in the current O139 strains was found to be unconventional.

Investigation of buffalopox outbreaks in Maharashtra State during 1992-1996

During 1992-96, outbreaks of buffalopox zoonosis were reported from different villages in Jalgaon, Dhule and Beed districts of Maharashtra State. In humans, pox lesions were observed on the hands whereas in affected buffaloes and cows the lesions were noticed mainly on the teats and udder. Twenty two virus strains were isolated from the skin scabs collected from infected humans and milch animals. Neutralizing antibodies were detected not only in the sera of affected humans but also in their contacts. Detection of antibodies in young individuals from endemic area, who were neither vaccinated for smallpox nor had any contact with buffaloes or history of any poxvirus disease, is suggestive of occurrence of subclinical infection. A few children who had no contact with infected animals also showed clinical manifestations with disseminated lesions on the face, arm and buttocks, and thus suspected to have acquired infection through their infected parents or other family members indicating a possible man to man transmission. Therefore, in the light of discontinuation of smallpox vaccination, buffalopox outbreaks need to be monitored carefully as this may emerge as a serious zoonotic disease in India.

Investigation of the outbreak of cholera in Alleppey & Palghat districts, south India

In May 1996, a massive outbreak of cholera occurred in Alleppey district of Kerala which spread to Palghat district by July 1996. Of the 575 patients hospitalized at the Alleppey Medical College hospital between May 1 and August 2, 1996, 30 deaths occurred with a case fatality rate of 5.2 per cent while of the 638 diarrhoea patients admitted at Agali PHC of Attapadi area in Palghat district, 30 (4.7%) deaths were recorded. Clinically, the patients had profuse watery diarrhoea with vomiting. The epidemic of cholera in Alleppey and Palghat districts was caused by V. cholerae O1 of the EITor biotype, Ogawa serotype which possessed both the ctxA and tcpA genes when examined by multiplex PCR. Gross contamination of water sources was incriminated as the cause of the epidemic.

A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging

We report a functional application of magnetic resonance imaging (MRI) for the quantitative description of left ventricular geometry through systole and diastole in normal anaesthetized Wistar rats that might be applicable for the analysis of chronic changes resulting from pathological conditions. Images of cardiac anatomy were acquired through planes both parallel and perpendicular to the principal cardiac axis at times that were synchronized to the R wave of the electrocardiogram. The images of the transverse sections were assembled into three-dimensional representations of left ventricular geometry at consecutive time points through the cardiac cycle. This confirmed the geometrical coherence of the data sets, that each slice showed circular symmetry, and that the images were correctly aligned with the appropriate anatomical axes. Different models for the three-dimensional geometry of the left ventricle were then tested against the epi- and endocardial surfaces reconstructed from images of the transverse sections of the left ventricle in both systole and diastole using least-squares minimizations in three dimensions. In agreement with previous reports in the human heart, an elliptical figure of revolution offered an optimal fit to the epicardial and endocardial geometry for the rat heart in diastole. This was in preference to models that used spherical, quartic or parabolic geometries. However, in contrast to contraction in the human heart, all these geometrical representations broke down during systolic ejection in the rat heart. We therefore introduced a more general hybrid model which described left ventricular geometry in terms of the variation of the radii r(z), independently determined for each slice, with its position z along the principal cardiac axis. The resulting function r(z) could then be described by a simple ellipsoid of revolution not only during diastole, but also throughout ventricular ejection. The findings also ruled out alternative geometrical representations. It was then possible additionally to reconstruct the luminal and total left ventricular volumes, wall thicknesses and ejection fractions through the cardiac cycle and to confirm that the predicted total ventricular wall volume was conserved throughout the cardiac cycle. Our hybrid model of cardiac geometry may thus be useful for non-invasive serial studies of chronic pathological changes that use the rat as a model experimental system.

A comparative study of silver binding nucleolar organiser regions (AgNORs) of breast lesions in histological sections and fine needle aspiration smears

The study presents a comparative profile of AgNOR dot counting in different types of breast lesions in histopathological (HP) sections and fine needle aspiration cytology (FNAC) smears. The breast lesions chosen were non-neoplastic lesion like fibroadenosis, benign neoplastic lesion like fibroadenoma and malignant neoplastic lesion like infiltrating duct carcinoma-grade 2. The AgNOR counts of non-neoplastic lesion were significantly less in number than the neoplastic lesions--both benign and malignant, in both the HP section and FNAC smear. But the counts did not show significant difference in the two neoplastic lesions eg, fibroadenoma and infiltrating duct carcinoma-grade 2, in both the HP section and FNAC smear. The appearance of the dots, as felt by the observers, were more discriminating between the three lesions, eg, uniform small compact centrally placed in fibroadenosis; mostly uniform small compact but occasional large irregular in fibroadenoma and large irregular marginally located in infiltrating duct carcinoma. Counting was easier and the appearance of the dots more easily discernible in FNAC smear than the HP section as the smear was monolayer and the malignant cells were easily detected from macrophages and stromal cells. But the tissue fluid or secretions or blood when present in the smear gave the smear a dirty background which was disturbing to the observers. Thus this AgNOR technique, when applied in HP section or FNAC smear, appears cost ineffective, lengthy and tedious procedure; did not offer absolute histochemical discriminant for malignancy from benignancy. But the shape and size distribution and appearance of the dots showing much variability in FNAC smear than the HP section, might be of some help in the diagnosis of malignancy and discriminating from benignancy.

Identification of an intronic enhancer that nullifies upstream repression of SPARC gene expression

The SPARC gene 5'flanking sequence has been shown to contain enhancer elements, but also negative control elements immediately upstream of the enhancer elements. Although these 5'enhancer elements are active in F9 and PYS-2 cells, their activities are nullified by the 5'repressor activity. In the present study we have identified within intron 1 between nucleotides (nt) +5000 and +5150 of the SPARC gene an enhancer element that bound to two transcription factors of 48 and 52 kDa and between nt +5000 and +5523 a DNase I hypersensitive site. Furthermore, a region containing the 3'intron 1 enhancer element, together with the 5'enhancer elements, neutralized the 5'repressor activity and stimulated efficient transcription. The resulting SPARC promoter activity is about equal in F9, differentiated F9 and PYS-2 cells. We consistently found that the rate of SPARC transcription is nearly the same in F9 and PYS-2 cells. Association of the 3'enhancer element in intron 1 with the DNase I hypersensitive site suggests that both play a role in regulating SPARC expression in vivo .

Al-Induced, 51-Kilodalton, Membrane-Bound Proteins Are Associated with Resistance to Al in a Segregating Population of Wheat

Incorporation of 35S into protein is reduced by exposure to Al in wheat (Triticum aestivum), but the effects are genotype-specific. Exposure to 10 to 75 [mu]M Al had little effect on 35S incorporation into total protein, nuclear and mitochondrial protein, microsomal protein, and cytosolic protein in the Al-resistant cultivar PT741. In contrast, 10 [mu]M Al reduced incorporation by 21 to 38% in the Al-sensitive cultivar Katepwa, with effects becoming more pronounced (31-62%) as concentrations of Al increased. We previously reported that a pair of 51-kD membrane-bound proteins accumulated in root tips of PT741 under conditions of Al stress. We now report that the 51-kD band is labeled with 35S after 24 h of exposure to 75 [mu]M Al. The specific induction of the 51-kD band in PT741 suggested a potential role of one or both of these proteins in mediating resistance to Al. Therefore, we analyzed their expression in single plants from an F2 population arising from a cross between the PT741 and Katepwa cultivars. Accumulation of 1,3-[beta]-glucans (callose) in root tips after 24 h of exposure to 100 [mu]M Al indicated that this population segregated for Al resistance in about a 3:1 ratio. A close correlation between resistance to Al (low callose content of root tips) and accumulation of the 51-kD band was observed, indicating that at least one of these proteins cosegregates with the Al-resistance phenotype. As a first step in identifying a possible function, we have demonstrated that the 51-kD band is most clearly associated with the tonoplast. Whereas Al has been reported to stimulate the activity of the tonoplast H+-ATPase and H+-PPase, antibodies raised against these proteins did not cross-react with the 51-kD band. Efforts are now under way to purify this protein from tonoplast-enriched fractions.

Transgenic elite indica rice plants expressing CryIAc delta-endotoxin of Bacillus thuringiensis are resistant against yellow stem borer (Scirpophaga incertulas)

Generation of insect-resistant, transgenic crop plants by expression of the insecticidal crystal protein (ICP) gene of Bacillus thuringiensis (Bt) is a standard crop improvement approach. In such cases, adequate expression of the most appropriate ICP against the target insect pest of the crop species is desirable. It is also considered advantageous to generate Bt-transgenics with multiple toxin systems to control rapid development of pest resistance to the ICP. Larvae of yellow stem borer (YSB), Scirpophaga incertulas, a major lepidopteran insect pest of rice, cause massive losses of rice yield. Studies on insect feeding and on the binding properties of ICP to brush border membrane receptors in the midgut of YSB larvae revealed that cryIAb and cryIAc are two individually suitable candidate genes for developing YSB-resistant rice. Programs were undertaken to develop Bt-transgenic rice with these ICP genes independently in a single cultivar. A cryIAc gene was reconstructed and placed under control of the maize ubiquitin 1 promoter, along with the first intron of the maize ubiquitin 1 gene, and the nos terminator. The gene construct was delivered to embryogenic calli of IR64, an elite indica rice cultivar, using the particle bombardment method. Six highly expressive independent transgenic ICP lines were identified. Molecular analyses and insect-feeding assays of two such lines revealed that the transferred synthetic cryIAc gene was expressed stably in the T2 generation of these lines and that the transgenic rice plants were highly toxic to YSB larvae and lessened the damage caused by their feeding.

Impaired basal glucose effectiveness in NIDDM: contribution of defects in glucose disappearance and production, measured using an optimized minimal model independent protocol

People with NIDDM are resistant to insulin. The present studies sought to determine whether the ability of glucose to regulate its own metabolism in the presence of basal insulin concentrations is impaired. To address this question, basal insulin concentrations were maintained constant with an exogenous insulin infusion, while endogenous hormone secretion was inhibited by somatostatin. The integrated glycemic response above baseline during identical prandial glucose infusions was greater (1,411 +/- 94 vs. 938 +/- 45 mmol/l per 5 h; P < 0.01) in the diabetic subjects than in the nondiabetic subjects, indicating a decrease in net glucose effectiveness. [6-3H]glucose also was infused to determine whether the decrease in net glucose effectiveness was due to a decrease in the ability of glucose to stimulate its own uptake and/or to suppress its own production. Despite identical rates of tracer infusion, the increment in plasma concentration of [6-3H]glucose was higher (4.50 +/- 0.29 vs. 3.16 +/- 0.21 x 10(5) dpm/ml per 5 h; P < 0.05) in the diabetic subjects than in the nondiabetic subjects. This was due to both a decrease (P < 0.05) in the ability of glucose to stimulate its own disappearance via mass action and to a greater (P < 0.01) inhibitory effect of glucose on its own clearance. The increase in glucose concentration resulted in prompt and comparable suppression of endogenous glucose production in both groups. Under these optimized conditions, indexes of glucose effectiveness calculated with both the "cold" and "hot" minimal models also were lower (P < 0.05) in the diabetic subjects than in the nondiabetic subjects and were highly correlated (r = 0.94-0.99; P < 0.001) with the indexes of glucose effectiveness calculated from the increments above baseline of glucose and [6-3H]glucose concentration. We conclude that the ability of glucose to regulate its own metabolism in the presence of basal insulin concentrations is abnormal in people with NIDDM.

Regulation of murine cytochrome oxidase Vb gene expression in different tissues and during myogenesis. Role of a YY-1 factor-binding negative enhancer

The mouse cytochrome oxidase (COX) Vb promoter contains three sequence motifs with partial or full consensus for YY-1 and GTG factor binding and a CArG box, located between positions -480 and -390. Individually, all three motifs stimulated transcription of the TKCAT promoter, and bound distinctly different proteins from the liver and differentiated C2C12 nuclear extracts. Collectively, these motifs, together with the downstream flanking sequence, -378 to -320, suppressed the transcription activity of heterologous promoters, thymidine kinase-chloramphenicol acetyltransferase (TKCAT) and COXIV/CAT. The transcription activities of both TKCAT and COXIV/CAT constructs were induced 3-4-fold during induced myogenesis of C2C12 cells. The downstream CArG-like motif binds transcription factor YY-1, while the upstream YY-1-like motif binds to a yet unidentified factor. Co-expression with intact YY-1, but not that lacking the DNA binding domain suppressed the transcriptional activity. Mutations targeted to the CArG-like motif abolished the suppressive effect of the negative enhancer and the inducibility of the promoter during myogenic differentiation. Our results suggest that the activity of the negative enhancer may determine the level of expression of the COX Vb gene in different tissues.

The intracisternal A-particle proximal enhancer-binding protein activates transcription and is identical to the RNA- and DNA-binding protein p54nrb/NonO

The long terminal repeats of murine intracisternal A particles (IAPs) contain an IAP proximal enhancer (IPE) element that is inactive in murine F9 embryonal carcinoma cells and active in the parietal endoderm cell line PYS-2. The element binds efficiently to a 60-kDa IPE-binding protein (IPEB) present in PYS-2 cells but poorly to F9 proteins, suggesting a role for IPEB in regulating IAP expression. We have purified calf thymus IPEB, which binds to the IPE and transactivates a reporter gene in HeLa cell extracts. Based on the peptide sequence of the purified calf IPEB, we have cloned a 420-bp cDNA and showed that the encoded protein is the homolog of human p54nrb and mouse NonO, which are characterized by the presence of two RNA recognition motifs. We show that p54nrb is an IPE-binding transcription activator with its DNA-binding and activation domains in the N- and C-terminal halves, respectively. The activation domain of p54nrb is active in HeLa, PYS-2, and F9 cells, whereas p54nrb as a whole molecule is active in HeLa and PYS-2 cells but not in F9 cells. Thus, the lack of activity of p54nrb in F9 cells is due to an ineffective DNA-binding domain. We demonstrate that p54nrb also binds to a pre-mRNA. Based on the close sequence relatedness of this protein to PSF, which is required for pre-mRNA splicing in vitro, we discuss the possibility that p54nrb has dual roles in transcription and splicing.

Bcl2 is the guardian of microtubule integrity

We have investigated the ability of several drugs commonly used in the treatment of human cancer to induce bcl2 phosphorylation and cell death in human cell lines derived from acute leukemia, lymphoma, breast cancer, and prostate cancer. The results of this analysis indicate that drugs affecting the integrity of microtubules induce bc12 phosphorylation, whereas anticancer drugs damaging DNA do not. Comparison of the effects of taxol and its analogue, taxotere, indicates that taxotere is capable of inducing bcl2 phosphorylation and apoptotic cell death at 100-fold lower concentrations than taxol. Induction of cancer cell death through phosphorylation of bcl2 thus provides an opportunity not only for more refined targeting of therapeutic drugs but for understanding of an important pathway leading to apoptosis. Phosphorylation of bcl2 in drug-treated cancer cells occurs in G2-M, the phase of the cell cycle in which this class of drugs is active. No induction of bcl2 phosphorylation occurs in chronic lymphocytic leukemia cells that overexpress bcl2 but are blocked at G0-G1. Thus, prevention of polymerization or depolymerization of cellular microtubules by this class of cancer therapeutic drugs causes phosphorylation of bcl2, abrogating the normal antiapoptotic function of bcl2 and initiating the apoptotic program in the cycling cancer cells; these results are consistent with a normal physiological role of bcl2 as "guardian of microtubule integrity."

Incorporation of T cell counterparts in the fusion partners for generation of human monoclonal antibodies from Staphylococcus aureus stimulated B lymphocytes

B cell growth and differentiation into immunoglobulin secreting cells is controlled by various cytokines and cell to cell contact with T cells. Fusion partner for human hybridoma therefore should accommodate all or some of these signaling systems to overcome the unique situation of MHC incompatibility, need for specific growth factors simultaneously taking into consideration the downstream processing of the product for the clinical use. We have thus directed our efforts towards the development of a fusion partner which would not need Epstein-Barr virus transformation of B cells prior to fusion. A nontransforming mitogen, formalinized Staphylococcus aureus (FSTA) was used for stimulating human B cells. Successful production of human IgM monoclonal antibody was achieved by incorporating Jurkat-4 cells in existing mouse human heterohybrid through fusion of these cells followed by fusion with human B cells. To accommodate chromosomes of both T and B cells after fusion, human myeloid precursor cells KG1a, and to incorporate T cell, HuT78 cells were fused. CD34+ and CD4+ hybrid of KG1a and HuT 78 cells-434 AM-when used as fusion partner could allow secretion of MAbs, however growth potential was low. SP2/0 cells were then incorporated in 434 AM cells to give myeloma environment to fused human B cells. Rabies virus neutralizing human IgG MAb secreting clone was generated by fusing FSTA stimulated human B cells with this fusion partner.

The role of an E box binding basic helix loop helix protein in the cardiac muscle-specific expression of the rat cytochrome oxidase subunit VIII gene

We have characterized the rat gene for muscle-specific cytochrome oxidase VIII (COX VIII(H)) and mapped the distal promoter region responsible for transcription activation in C2C12 skeletal myocytes and H9C2 cardiomyocytes. In both cell types, the promoter elements responding to the induced differentiation of myocytes map to two E boxes, designated as E1 and E2 boxes with a core sequence of CAGCTG. Gel mobility shift analysis showed that both E1 and E2 box motifs form complexes with nuclear extracts from H9C2 cardiomyocytes that were supershifted with monoclonal antibody to E2A but not with antibody to myo-D. Extracts from induced and uninduced H9C2 cardiomyocytes yielded different gel mobility patterns and also different E2A antibody supershifts suggesting a difference in the DNA-bound protein complexes cross-reacting with the E2A antibody. Transcriptional activity of the promoter construct containing intact E boxes was inhibited by coexpression with Id in differentiated H9C2 cardiomyocytes. Our results show the involvement of an E box binding basic helix loop helix protein in the cardiac muscle-specific regulation of the COX VIII(H) promoter.

Characterization of the protein kinase C signal transduction pathway in cisplatin-sensitive and -resistant human small cell lung carcinoma cells

Protein kinase C (PKC) influences cellular sensitivity to cis-diamminedichloroplatinum(II) (cDDP). We have investigated whether the PKC signal transduction pathway is affected during the development of cellular resistance to cDDP. Activators of PKC, such as phorbol 12,13-dibutyrate (PDBu), enhanced the sensitivity of human small cell lung cancer H69 cells to cDDP by 2-fold but had no effect on the sensitivity of cDDP-resistant H69 cells (H69/CP) to cDDP. The maximum sensitization was achieved with 10 nM PDBu and blocked by down-regulation of PKC with higher concentrations of PDBu (1 microM) or bryostatin 1 (0.1 microM). PKC activity was decreased significantly in H69/CP cells compared to the drug-sensitive variant. A similar reduction in PKC activity was noted in ovarian carcinoma 2008 cells that were resistant to cDDP. A modest decrease in PKC activity was also observed in etoposide-resistant H69 (H69/VP-16) cells but not in Taxol-resistant H69 cells or bleomycin-resistant human head and neck carcinoma A-253 cells. H69 cells expressed conventional PKC alpha and-beta, novel PKC delta, atypical PKC zeta and-iota, and novel/atypical PKC mu. A decrease in cPKC alpha and-beta and an increase in nPKC delta were associated with the cDDP-resistant phenotype. The abundance of aPKC zeta or-iota was unaffected. H69/ VP-16 cells also displayed a reduction in cPKC beta and an increase in nPKC delta. Taxol-resistant H69 cells had no alteration in the expression of any of the PKC isozymes. Thus, a reduction in cPKCs and an increase in nPKC may be associated with cDDP resistance.

Temporal shifts in traits of Vibrio cholerae strains isolated from hospitalized patients in Calcutta: a 3-year (1993 to 1995) analysis

This study presents results of a surveillance on cholera conducted with hospitalized patients admitted to the Infectious Diseases Hospital, Calcutta, India, from January 1993 to December 1995. The O139 serogroup of Vibrio cholerae dominated in 1993 but was replaced by O1 as the dominant serogroup in 1994 and 1995. The isolation rate of V. cholerae non-O1 non-O139 did not exceed 4.9% throughout the study period, while the isolation rate of the O139 serogroup in 1994 and 1995 was below 9%. No temporal clustering of any non-O1 non-O139 serogroup was observed. With the exception of 1 strain, none of the 64 strains belonging to the non-O1 non-O139 serogroup hybridized with ctx, zot, and ace gene probes, while 97.3 and 97.7% of the O139 and O1 strains, respectively, hybridized with all the three probes. Multiplex PCR studies revealed that all the O1 strains belonged to the EIT or biotype. There was a progressive increase in the cytotoxic response on CHO and HeLa cells evoked by culture supernatants of strains of V. cholerae non-O1 non-O139 isolated during 1994 and 1995 compared with the response evoked by those isolated in 1993. Dramatic shifts in patterns of resistance to antibiotics between strains of V. cholerae belonging to different serogroups and within strains of a serogroup isolated during different time periods were observed. There was a discernible increase in the incidence of multidrug-resistant strains of V. cholerae O1 isolated in 1994 and 1995 compared with that in 1993. On the basis of the results of this study, we predict the possibility of newer variants of V. cholerae emerging in the future.

Peripheral blood mononuclear cells of patients with Indian visceral leishmaniasis suppress natural killer cell activity in vitro

Peripheral blood mononuclear cells (PBMC) of patients with Indian visceral leishmaniasis (VL) suppressed the natural killer cell (NK) activity of normal human PBMC in vitro in a dose-dependent manner. Adherent monocytes, but not the non-adherent lymphocytes of VL patients suppressed NK activity through soluble mediators. The level of suppression seen in different patients was variable.

Effects of a change in the pattern of insulin delivery on carbohydrate tolerance in diabetic and nondiabetic humans in the presence of differing degrees of insulin resistance

While it is well established that people with non-insulin dependent diabetes mellitus have defects in both insulin secretion and action, the relative contribution of each to glucose intolerance is not known. Therefore, nondiabetic (lean and obese) and non-insulin dependent diabetes mellitus subjects were studied on two occasions. On each occasion, insulin secretion was inhibited with somatostatin and glucose was infused in a pattern and amount that mimicked the systemic delivery rate normally observed after ingestion of 50 g of glucose. Insulin also was infused so as to mimic postprandial insulin profiles observed in separate groups of diabetic and nondiabetic subjects after food ingestion. Glucose turnover was measured using the isotope dilution method. A delayed pattern of insulin delivery (i.e., a "diabetic" insulin profile) led to higher (P < 0.05) glucose concentrations in all groups; however, the effects were transient, resulting in only a modest increase in the integrated glycemic responses. An isolated defect in insulin action had little effect on peak glucose concentration; however, it prolonged the duration of hyperglycemia, leading to a 2.5-4.2-fold increase (P < 0.05) in the integrated glycemic response. A combined defect in the pattern of insulin secretion and action was additive rather than synergistic. Both defects caused hyperglycemia by altering suppression of endogenous glucose release and stimulation of glucose disposal. Whereas obese diabetic and nondiabetic subjects had comparable defects in glucose clearance, non-insulin dependent diabetes mellitus subjects also had defects in hepatic insulin action. Thus, abnormalities in the pattern of insulin secretion and action alone or in combination impair glucose tolerance. An isolated defect in insulin action has a more pronounced and prolonged effect than does an isolated change in the pattern of insulin secretion. Hepatic and extrahepatic insulin resistance results in marked and sustained hyperglycemia.