Stability of the human polymerase δ holoenzyme and its implications in lagging strand DNA synthesis

In eukaryotes, DNA polymerase δ (pol δ) is responsible for replicating the lagging strand template and anchors to the proliferating cell nuclear antigen (PCNA) sliding clamp to form a holoenzyme. The stability of this complex is integral to every aspect of lagging strand replication. Most of our understanding comes from Saccharomyces cerevisae where the extreme stability of the pol δ holoenzyme ensures that every nucleobase within an Okazaki fragment is faithfully duplicated before dissociation but also necessitates an active displacement mechanism for polymerase recycling and exchange. However, the stability of the human pol δ holoenzyme is unknown. We designed unique kinetic assays to analyze the processivity and stability of the pol δ holoenzyme. Surprisingly, the results indicate that human pol δ maintains a loose association with PCNA while replicating DNA. Such behavior has profound implications on Okazaki fragment synthesis in humans as it limits the processivity of pol δ on undamaged DNA and promotes the rapid dissociation of pol δ from PCNA on stalling at a DNA lesion.During S-phase of the cell cycle, genomic DNA must be faithfully copied in a short period. Replicative DNA polymerases (pols) alone are distributive and must anchor to ring-shaped sliding clamps to achieve the high degree of processivity required for efficient DNA replication. The highly conserved toroidal structure of sliding clamps has a central cavity large enough to encircle double-stranded DNA (dsDNA) and slide freely along it. Thus, such an association effectively tethers the pol to DNA, substantially increasing the extent of continuous replication. The eukaryotic sliding clamp, proliferating cell nuclear antigen (PCNA), is trimer of identical subunits aligned head-to-tail, forming a ring with two structurally distinct faces. Each subunit consists of two independent domains connected by an interdomain connecting loop (IDCL). The “front” face of the homotrimeric PCNA ring contains all IDCLs and is a platform for interaction with the eukaryotic replicative pols, ε and δ, which are responsible for the faithful replication of the leading and lagging strands, respectively (1, 2). Specifically, the well-conserved PCNA-interacting peptide (PIP) box within replicative pols makes extensive contact with an IDCL of PCNA and displays conserved residues that “plug” into the proximal hydrophobic patches. The amino acid sequence of a canonical PIP box is QXXhXXaa, where X represents any amino acid, h is a hydrophobic residue (usually L, I, or M), and a is an aromatic residue (usually F or Y) (3).Unlike the leading strand, the lagging strand is synthesized discontinuously in short Okazaki fragments that are processed and ligated together to form a continuous strand (4). In eukaryotes, each Okazaki fragment is initiated by the bifunctional DNA pol α/primase complex that lays down cRNA/DNA hybrid primers every 100–250 nucleotides (nt) on the exposed template for the lagging strand. The intermittent single-stranded DNA (ssDNA) is protected from cellular nucleases by replication protein A (RPA), a ssDNA binding protein that also prevents formation of alternative DNA structures. The clamp loader, replication factor C (RFC), recognizes these hybrid primers abutted by RPA and loads PCNA onto each such that the front face of the clamp is oriented toward the 3′ end of the nascent primer/template (P/T) junction where DNA synthesis will initiate. An incoming pol δ subsequently captures the loaded PCNA ring, forming a holoenzyme, and DNA synthesis initiates (2, 5).The stability of the lagging strand holoenzyme is integral to various aspects of Okazaki fragment synthesis. For eukaryotes, most of our understanding comes from studies in Saccharomyces cerevisae, where the three-subunit pol δ is extremely stable with PCNA on DNA (k_off < 2 × 10⁻³ s⁻¹, t_1/2 > 5 min). Once DNA synthesis is initiated from a nascent primer, the dramatically slow k_off ensures every nucleotide within a given Okazaki fragment is faithfully duplicated before dissociation. On the other hand, such high stability necessitates an active mechanism for displacement of pol δ once DNA synthesis stops (6, 7). This situation arises when a pol δ holoenzyme encounters either the 5′ RNA end of a downstream Okazaki fragment (pol recycling) or distortions to the native sequence that it cannot accommodate (pol exchange), such as common byproducts of UV radiation exposure (8). Pol recycling allows the scarce pol δ to be reused during S-phase, whereas pol exchange permits a specialized pol to bind to PCNA and synthesize past the offending damage [translesion DNA synthesis (TLS)] so that pol δ may resume synthesis (9–12). However, studies on the human pol δ holoenzyme are lacking, and hence, the mechanisms by which polymerase recycling and exchange occur are unknown. To gain insight, we designed a unique kinetic assay to measure the stability of the pol δ holoenzyme. Surprisingly, the results indicate that human pol δ maintains a loose association with PCNA. Such behavior has profound implications on lagging strand synthesis as it limits the extent of processive DNA synthesis and promotes the rapid dissociation of pol δ from PCNA on stalling.     

Inhibition of aortic histamine synthesis by α-hydrazinohistidine inhibits increased aortic albumin accumulation in experimental diabetes in the rat

Summary We examined the interrelationship between inhibition of aortic histamine synthesis through inhibition of aortic histidine decarboxylase and intra-aortic albumin accumulation in rats made diabetic by a jugular vein injection of 60 mg/kg of streptozotocin under ether anesthesia. Animals were held for 4 weeks following overt manifestation of diabetes. At the end of 3 weeks, at least six animals in each of the diabetic and non-diabetic groups received intra-peritoneal injections of -hydrazinohistidine (25 mg/kg at 12 h) for the last 7 days. Aortic albumin accumulation was measured by quantification of aortic uptake of fluorescein isothiocyanate conjugated to rat serum albumin injected in the jugular vein 1 h before sacrifice. The aortic albumin mass transfer and flux rates of the diabetic group were more than 300% higher than that of the control group; -hydrazinohistidine treated diabetic rats had aortic albumin mass transfer rates equivalent to control values. The aortic albumin content was nearly tenfold higher in untreated diabetic rats, but again treatment with -hydrazinohistidine returned this to control values. These data offer strong support to the premise that accelerated aortic histamine synthesis, which occurs in experimental diabetes, is an important mediator of increased aortic macromolecule uptake, and as such, may be one component of the multitude of factors responsible for increased susceptibility of atherosclerosis among individuals having diabetes mellitus.     

What are the barriers to primary prevention of type 2 diabetes in black and minority ethnic groups in the UK? A qualitative evidence synthesis

Background

This review aimed to synthesise available qualitative evidence on barriers and facilitators to the implementation of community based lifestyle behaviour interventions to reduce the risk of diabetes in black and minority ethnic (BME) groups in the UK.

Methods

A search of medical and social science databases was carried out and augmented by hand-searching of reference lists and contents of key journals. Qualitative evidence was synthesised thematically.

Results

A total of 13 papers varying in design and of mainly good quality were included in the review. A limited number of intervention evaluations highlighted a lack of resources and communication between sites. A lack of understanding by providers of cultural and religious requirements, and issues relating to access to interventions for users was reported. Behaviour change was impeded by cultural and social norms, and resistance to change. There were variations in the way dietary change and physical activity was approached by different groups and contrasting practices between generations.

Conclusions

Qualitative data provided insight into the ways that providers might improve or better design future interventions. Acknowledgement of the way that different groups approach lifestyle behaviours may assist acceptability of interventions.     

Glycogen synthesis kinase-3β involves in the analgesic effect of liraglutide on diabetic neuropathic pain

AimsExplore whether Glycogen synthesis kinase-3β (GSK3β) involved in the analgesic effect of liraglutide on diabetic neuropathic pain (DNP).MethodsDNP was induced by streptozocin (STZ) in WT and GSK3β(S9A) mice, which carried a constitutively active form of GSK3β. DNP mice were intracerebroventricularly injected with liraglutide 5 weeks after STZ injection. The behavior of neuropathic pain was evaluated 2 h after drugs administration. The microglial activation and the expression of NOD-like receptor protein 3 (NLRP3) in microglia in cortex were evaluated. The role of GSK3β in the inhibitory effect of liraglutide on the NLRP3 inflammasome was explored in BV2 microglia.ResultsIntracerebroventricular administration of liraglutide significantly relieved neuropathic pain and inhibited the activation of cortical microglia in WT mice with DNP. But the effect of liraglutide disappeared in GSK3β(S9A) mice. In BV2 microglia, GSK3β inhibitor significantly suppressed NLRP3 inflammasome activation. And activating GSK3β through GSK3β(S9A) lentivirus significantly blocked the inhibitory effect of liraglutide on NLRP3 inflammasome in BV2 microglia. Intracerebroventricular administration of liraglutide significantly inhibited the expression of NLRP3 in cortex microglia of DNP group in WT mice but failed in GSK3β(S9A) mice.ConclusionGSK3β involves in the analgesic effect of liraglutide on DNP through NLRP3 inflammasome in microglia.     

17β-Estradiol is critical for the preovulatory induction of prostaglandin E(2) synthesis in mice

Aromatase-deficient (ArKO) mice are totally anovulatory due to insufficient estrogen production. However, sequential administrations of high doses of 17β-estradiol (E2) and gonadotropins were found to induce ovulation in these mice. Here, we examined how the ovulatory stimulation for ArKO mice alters the expressions of genes related to prostaglandin (PG) E(2) metabolism and ovarian contents of PGE(2), as PGE(2) is one of the critical mediators of ovulatory induction. The ovulatory stimulation significantly increased mRNA expressions of prostaglandin-endoperoxide synthase 2, PGE(2) receptor type 4 and sulfotransferase family 1E, member 1, in preovulatory ArKO ovaries. In contrast, it suppressed the mRNA expression of 15-hydroxyprostaglandin dehydrogenase. Furthermore, significant elevation in the PGE(2) contents was detected in the preovulatory ovaries of ArKO mice after stimulation with E2 plus ovulatory doses of gonadotropins. Thus, these analyses demonstrate a requirement of E2 for the preovulatory enhancement of PGE(2) synthesis, leading to future success in ovulation.     

The effects of angiotensin Ⅱ on the synthesis of albumin and type Ⅰ collagen in human hepatic cells

Objective To investigate the effects of angiotensin Ⅱ (AngⅡ) on the expression of albumin and the synthesis of type Ⅰ collagen in human normal hepatic cells. Methods HL-7702 cells (human normal hepatocyte) were cultured and divided into control group, Ang Ⅱ treated group, an AngⅡ+irbesartan (co-stimulated) group. The expressions of albumin and type Ⅰ collagen were detected by immunofluorescence and Western blotting, respectively. The mRNA level of type Ⅰ collagen was measured by real time-PCR(qRT-PCR). Results After stimulated with 10-7 mol/L Ang Ⅱ for 72 hours, the expression of albumin significantly decreased in Ang Ⅱ treated group compared with control group (0.85±0.11 vs 1. 41±0.23,P=0.000), while the mRNA expression increased in AngⅡ treated group compared with control group (1.00±0.08 vs 3.72±0.19,P=0.000). In costimulated group, however, the expression of albumin significantly increased (0.85 ± 0.11 vs 1.38 ±0.32,P=0.000),and mRNA expression (3. 72±0.19 vs 2.86±0.13,P=0.000) and synthesis of type Ⅰ collagen were reduced when compared with Ang Ⅱ treated group. Conclusions The reduction of albumin and elevated systhesis of type Ⅰ collagen in HL-7702 cells are induced via Ang Ⅱ AT1 receptor.     

The effects of angiotensin Ⅱ on the synthesis of albumin and type Ⅰ collagen in human hepatic cells

Objective To investigate the effects of angiotensin Ⅱ (AngⅡ) on the expression of albumin and the synthesis of type Ⅰ collagen in human normal hepatic cells. Methods HL-7702 cells (human normal hepatocyte) were cultured and divided into control group, Ang Ⅱ treated group, an AngⅡ+irbesartan (co-stimulated) group. The expressions of albumin and type Ⅰ collagen were detected by immunofluorescence and Western blotting, respectively. The mRNA level of type Ⅰ collagen was measured by real time-PCR(qRT-PCR). Results After stimulated with 10-7 mol/L Ang Ⅱ for 72 hours, the expression of albumin significantly decreased in Ang Ⅱ treated group compared with control group (0.85±0.11 vs 1. 41±0.23,P=0.000), while the mRNA expression increased in AngⅡ treated group compared with control group (1.00±0.08 vs 3.72±0.19,P=0.000). In costimulated group, however, the expression of albumin significantly increased (0.85 ± 0.11 vs 1.38 ±0.32,P=0.000),and mRNA expression (3. 72±0.19 vs 2.86±0.13,P=0.000) and synthesis of type Ⅰ collagen were reduced when compared with Ang Ⅱ treated group. Conclusions The reduction of albumin and elevated systhesis of type Ⅰ collagen in HL-7702 cells are induced via Ang Ⅱ AT1 receptor.     

Autocrine regulation of ecdysone synthesis by β3-octopamine receptor in the prothoracic gland is essential for Drosophila metamorphosis

In Drosophila, pulsed production of the steroid hormone ecdysone plays a pivotal role in developmental transitions such as metamorphosis. Ecdysone production is regulated in the prothoracic gland (PG) by prothoracicotropic hormone (PTTH) and insulin-like peptides (Ilps). Here, we show that monoaminergic autocrine regulation of ecdysone biosynthesis in the PG is essential for metamorphosis. PG-specific knockdown of a monoamine G protein-coupled receptor, β3-octopamine receptor (Octβ3R), resulted in arrested metamorphosis due to lack of ecdysone. Knockdown of tyramine biosynthesis genes expressed in the PG caused similar defects in ecdysone production and metamorphosis. Moreover, PTTH and Ilps signaling were impaired by Octβ3R knockdown in the PG, and activation of these signaling pathways rescued the defect in metamorphosis. Thus, monoaminergic autocrine signaling in the PG regulates ecdysone biogenesis in a coordinated fashion on activation by PTTH and Ilps. We propose that monoaminergic autocrine signaling acts downstream of a body size checkpoint that allows metamorphosis to occur when nutrients are sufficiently abundant.In many animal species, the developmental transition is a well-known biological process in which the organism alters its body morphology and physiology to proceed from the juvenile growth stage to the adult reproductive stage. For example, in mammals, puberty causes a drastic change from adolescent to adulthood, whereas in insects, metamorphosis initiates alteration of body structures to produce sexually mature adults, a process accompanied by changes in habitat and behavior. These developmental transitions are primarily regulated by steroid hormones, production of which is regulated coordinately by developmental timing and nutritional conditions (1–3). How these processes are precisely regulated in response to developmental and environmental cues is a longstanding question in biology.In holometabolous insects, the steroid hormone ecdysone plays a pivotal role in metamorphosis. In Drosophila, metamorphic development from the third-instar larva into the adult, through the prepupa and pupa, initiates 90–96 h after hatching (hAH) at 25 °C under a standard culture condition (4). At the onset of the larval–prepupal transition, ecdysone is produced in the prothoracic gland (PG) and then converted into its active form, 20-hydroxyecdysone (20E), in the peripheral organs. The activities of 20E terminate larval development and growth and initiates metamorphosis (5). Ecdysone biosynthesis is regulated in the PG by neuropeptides, enabling modulation of the timing of 20E pulses during development (2–4). The best-known stimulator of ecdysone biosynthesis is prothoracicotropic hormone (PTTH), which is produced by neurons in the CNS. PTTH activates the receptor tyrosine kinase Torso in the PG to stimulate expression of ecdysone biosynthetic genes through the Ras85D/Raf/MAPK kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway (6, 7). Insulin-like peptides (Ilps), members of another class of neuron-derived factors, activate PI3K in the PG, resulting in production of ecdysone biosynthetic proteins (8–11). The Activin/transforming growth factor-β (TGF-β) signaling pathway is also required in the PG for the expression of PTTH and Ilps receptors, although to date it remains unclear which organ produces the ligand that acts on the PG (12).In addition to these neuropeptides, the larval–prepupal transition is modulated by environmental cues such as nutritional conditions that influence larval body size. For example, at 56 hAH, early third-instar larvae attain the minimal viable weight (MVW), at which sufficient nutrition is stored in larvae to ensure their survival through metamorphosis (2, 13, 14). After attaining MVW, larvae pass another checkpoint, critical weight (CW), defined as the minimum larval size at which starvation no longer delays the larval–prepupal transition (2, 13, 14). In Drosophila, both checkpoints occur almost simultaneously, making it difficult to distinguish them (2). However, CW is regarded as a body size checkpoint that initiates metamorphosis and is therefore believed to ultimately modulate ecdysone production in the PG. However, its downstream effectors and signaling pathway remain elusive.Based on data obtained in Manduca and Bombyx (15, 16), a G protein-coupled receptor (GPCR) has long been postulated to be essential for ecdysone biosynthesis in the PG. However, this GPCR and its ligand have not yet been identified. Here we show that monoaminergic autocrine signaling through a GPCR, β3-octopamine receptor (Octβ3R), plays an essential role in ecdysone biosynthesis to execute the larval–prepupal transition. Octβ3R is also required for activation of PTTH and Ilps signaling. We propose that this autocrine system acts downstream of the CW checkpoint to allow the larval–prepupal transition. We speculate that monoamines play an evolutionarily conserved role in the regulation of steroid hormone production during developmental transitions.     

From the Cover: Human Pol ζ purified with accessory subunits is active in translesion DNA synthesis and complements Pol η in cisplatin bypass

DNA polymerase ζ (Pol ζ) is a eukaryotic B-family DNA polymerase that specializes in translesion synthesis and is essential for normal embryogenesis. At a minimum, Pol ζ consists of a catalytic subunit Rev3 and an accessory subunit Rev7. Mammalian Rev3 contains >3,000 residues and is twice as large as the yeast homolog. To date, no vertebrate Pol ζ has been purified for biochemical characterization. Here we report purification of a series of human Rev3 deletion constructs expressed in HEK293 cells and identification of a minimally catalytically active human Pol ζ variant. With a tagged form of an active Pol ζ variant, we isolated two additional accessory subunits of human Pol ζ, PolD2 and PolD3. The purified four-subunit Pol ζ4 (Rev3–Rev7–PolD2–PolD3) is much more efficient and more processive at bypassing a 1,2-intrastrand d(GpG)-cisplatin cross-link than the two-subunit Pol ζ2 (Rev3–Rev7). We show that complete bypass of cisplatin lesions requires Pol η to insert dCTP opposite the 3′ guanine and Pol ζ4 to extend the primers.DNA polymerase ζ (Pol ζ), composed of the catalytic Rev3 and accessary Rev7 subunits, is an error-prone DNA translesion polymerase that causes both spontaneous and DNA damage-induced mutagenesis (1, 2). More than two-thirds of the 1,504 residues in yeast Rev3 share sequence homology with all B-family DNA polymerases, including Pols α, δ, and ε, which are responsible for the bulk of high-fidelity genomic replication in eukaryotes (3). Unlike the typical B-family polymerases, Pol ζ lacks an intrinsic 3′–5′ exonuclease activity and thus has no proofreading function (2). Human homologs of REV3 (REV3L) and REV7 (MAD2L2; hereafter referred to as REV7) genes were identified shortly after yeast Pol ζ was characterized. Human Rev3 contains 3,130 residues and is twice as large as the yeast counterpart (4). Human and yeast Rev7 are homologous (5) and bear sequence similarity to the mitotic checkpoint proteins Mad2 (6). Unlike Saccharomyces cerevisiae REV3 and REV7 genes, which are nonessential and whose knockout leads only to a decreased rate of damage-induced mutagenesis (7, 8), Rev3l knockout in mice is embryonic-lethal (9), and mouse Rev3l^−/− embryonic stem cells are not viable (10, 11). Human and mouse cell cultures obtained from conditional Rev3l knockout show genome instability and growth defects without an external challenge of DNA damage (12–14). DNA pol ζ is apparently essential for normal cell proliferation and embryogenesis in mammals.Translesion synthesis (TLS) and DNA-damage-induced mutagenesis are the best-characterized functions of Pol ζ. Absence of the yeast REV3 gene leads to sensitivity to UV light and intrastrand and interstrand cross-linking agents (2, 15). DNA Pol ζ has been shown to induce multiple base substitutions as well as more complex mutations in yeast (7, 16, 17) and may contribute to hypermutation in Ig genes in mammals (18, 19). The TLS function of DNA Pol ζ has been implicated in its role of mediating resistance to platinum-based chemotherapies (20–22). Owing to the conservation of B-family DNA polymerases, a distorted DNA template base is unlikely to be accommodated in the active site of DNA Pol ζ. In fact, yeast DNA Pol ζ is unable to insert a nucleotide opposite either a cis–syn thymine or a 6-4 photoproduct (23). Genetic data indicate that a complete lesion bypass event may require two TLS DNA polymerases (24)—one for nucleotide incorporation opposite a lesion (insertion step) and the other for the subsequent primer extension (extension step). The insertion step of TLS is often accomplished by a Y-family polymerase, whose active site is uncommonly large, solvent-exposed, and flexible (25). Studies of another B-family TLS DNA polymerase from Escherichia coli (Pol II) show that it efficiently extends a DNA primer after a lesion by looping out the damaged DNA template strand, leading to frameshift and mixed-type mutations (26).In budding yeast, REV3 has been shown to be epistatic with POL32, a subunit of DNA Pol δ. Inactivating either REV3 or POL32 leads to reduced spontaneous mutagenesis (27–29). As with all eukaryotic B-family DNA polymerases, Rev3 contains a Cys-rich C-terminal domain (CTD) (30–33), which forms a zinc-finger domain followed by a [4Fe–4S] cluster (34). In Pol α, δ, and ε, each CTD interacts with its specific accessary subunits (32, 35). Recently, three groups have independently shown that the [4Fe–4S] cluster of yeast Rev3 interacts with Pol31 and Pol32 subunit (36), thus forming an stoichiometric four-subunit Pol ζ (Pol ζ4; Rev3–Rev7–Pol31–Pol32) (23, 37, 38). Baranovskiy et al. further showed that the CTDs of human Pol ζ and δ share the same accessary subunits p50 and p66, homologs of yeast Pol31 and Pol32, respectively (37). The interaction between yeast Rev3 and Pol31 is reported to be direct, and Pol32 is essential to stabilize Pol31 and, furthermore, via its interactions with proliferating cell nuclear antigen (PCNA), recruits and activates Pol ζ to carry out TLS (38). The catalytic activity of yeast Pol ζ is improved by the presence of Pol31 and Pol32 (23, 38).Purification and characterization of Pol ζ has so far been limited to the yeast protein. Perhaps because of its large size, mammalian Pol ζ has not been purified for biochemical characterization. To overcome this roadblock, we coexpressed human REV3L and REV7 in mammalian cells in culture. Initially, very low expression level and heterogeneity was encountered, but these problems were solved by targeted deletion of various internal segments of human REV3L. We succeeded in purifying an active two-subunit form of human Pol ζ (Pol ζ2). By differential pull-down experiments using Pol ζ2 variants with and without the CTD of Rev3, we isolated two CTD-dependent Pol ζ accessary subunits, PolD2 and PolD3. We report here purification of an active form of human four-subunit Pol ζ4 and the collaboration of two TLS polymerases, Pol η and Pol ζ, in lesion bypass.     

β-Thalassemia Haplotypes in Romania in the Context of Genetic Mixing in the Mediterranean Area

The purpose of this meta-study was to investigate β-thalassemia (β-thal) mutations and their chromosomal background in order to highlight the origin and spread of thalassemia alleles in the European and Mediterranean areas. Screening of more than 100 new Romanian β-thal alleles was also conducted. The results suggest an ancient introduction of mutations at codon 39 (C?>?T) (HBB: c.118C?>?T) and IVS-I-6 (T?>?C) (HBB: c.92?+?6T?>?C) in Romania. A comparative study was performed based on restriction fragment length polymorphism (RFLP) haplotypes associated with β-thal mutations in Romania and in Mediterranean countries. Each common β-thal allele from different populations exhibits a high degree of haplotype similarity, a sign of a clear unicentric origin for the IVS-I-110 (G?>?A) (HBB: c.93-21G?>?A), IVS-I-6, IVS-II-745 (C?>?G) (HBB: c.316-106C?>?G) and codon 39 mutations (the 17a [+?????????+?+], 13c [???+?+???????+], 17c [?+???????????+] and 14a [??+?+???+?+?+?] ancestral RFLP background, respectively), followed by recurrent recombination events. This study also showed that geographic distances played a major role in shaping the spread of the predominant β-thal alleles, whereas no genetic boundaries were detected between broad groups of populations living in the Middle East, Europe and North Africa. The analyses revealed some discrepancies concerning Morocco and Serbia, which suggest some peculiar genetic flows. Marked variations in β^A were observed between Southeast Asia and the Mediterranean, whereas a relative genetic homogeneity was found around the Mediterranean Basin. This homogeneity is undoubtedly the result of the high level of specific historic human migrations that occurred in this area.     

Does the presence of diabetic nephropathy in parents influence the metabolic response in the offspring?

Non-insulin dependent (Type 2) diabetes mellitus (NIDDM) and long-term complications such as nephropathy have a strong genetic predisposition. Insulin resistance is thought to be a pathogenetic factor, predisposing genetically prone individuals to develop the microvascular complications of diabetes. To test these hypotheses, two groups of young individuals were studied: 28 offspring of parents having NIDDM and diabetic nephropathy (group 1) aged 29.5 ± 6.1 years, BMI 25.2 ± 4.7 kg m⁻² and 31 offspring of diabetic parents with no history of nephropathy, aged 31.6 ± 4.1 years and BMI 26.3 ± 4.9 kg m⁻² (group 2). All underwent a standard oral glucose tolerance test with measurement of serum insulin levels and serum lipid profile. Urine albumin:creatinine ratio (A/C ratio) and blood pressure were also recorded. Diabetes was detected in 2/28 (7.1 %) and 3/31 (9.7 %) and IGT was detected in 5/28 (25 %) and 8/31 (25 %) of groups 1 and 2, respectively. These differences were not statistically significant, but were higher than in a group of non-diabetic controls with healthy parents. Comparison of the normoglycaemic subjects (19 and 20 in group 1 and 2, respectively) showed no significant differences between blood pressure readings, fasting and 2 h plasma glucose, and lipid profiles. Plasma insulin values, fasting and 2 h, and the area under the graph were also similar in both groups, indicating an absence of higher insulin response in group 1 in comparison with group 2. These values were also not different from those in the non-diabetic controls. A delay in insulin response to glucose was noted in many of the offspring as indicated by a low ΔI/ΔG at 30′. We conclude that offspring of diabetic parents with nephropathy do not show higher risk of glucose intolerance or insulin resistance compared to those with diabetic parents without nephropathy. The relatively high plasma glucose values in the presence of normal insulin secretion in both groups of offspring of diabetic parents suggest the presence of insulin resistance. © 1997 John Wiley & Sons, Ltd.     

Gastro-entero-hepatology in the New Millennium

The global prospects for gastroenterology are excellent. The subspecialty involves the largest area of body surface, the largest endocrine organ, the largest neuronal organ (with 200 million neurones), and the largest immune organ (with 50 % of all lymphocytes); it includes by far the largest number of diseases, many still unexplored, and the largest oncological patient load. Gastroenterology/hepatology lies at the cross-roads between internal medical and surgical specialties.