We have cloned a novel pancreatic beta cell and neuroendocrine cell-specific calcium-binding protein termed secretagogin. The cDNA obtained by immunoscreening a human pancreatic cDNA library using the recently described murine monoclonal antibody D24 contains an open reading frame of 828 base pairs. This codes for a cytoplasmic protein with six putative EF finger hand calcium-binding motifs. The gene could be localized to chromosome 6 by alignment with GenBank genomic sequence data. Northern blot analysis demonstrated abundant expression of this protein in the pancreas and to a lesser extent in the thyroid, adrenal medulla, and cortex. In addition it was expressed in scant quantity in the gastrointestinal tract (stomach, small intestine, and colon). Thyroid tissue expression of secretagogin was restricted to C-cells. Using a sandwich capture enzyme-linked immunosorbent assay with a detection limit of 6.5 pg/ml, considerable amounts of constitutively secreted protein could be measured in tissue culture supernatants of stably transfected RIN-5F and dog insulinoma (INS-H1) cell clones; however, in stably transfected Jurkat cells, the protein was only secreted upon CD3 stimulation. Functional analysis of transfected cell lines expressing secretagogin revealed an influence on calcium flux and cell proliferation. In RIN-5F cells, the antiproliferative effect is possibly due to secretagogin-triggered down-regulation of substance P transcription.

Aims/hypothesisThe aim of the study was to compare the effect of six (A6 regimen) vs two meals a day, breakfast and lunch (B2 regimen), on body weight, hepatic fat content (HFC), insulin resistance and beta cell function.MethodsIn a randomised, open, crossover, single-centre study (conducted in Prague, Czech Republic), we assigned 54 patients with type 2 diabetes treated with oral hypoglycaemic agents, both men and women, age 30–70 years, BMI 27–50 kg/m2 and HbA1c 6–11.8% (42–105 mmol/mol), to follow two regimens of a hypoenergetic diet, A6 and B2, each for 12 weeks. Randomisation and allocation to trial groups (n = 27 and n = 27) were carried out by a central computer system. Individual calculations of energy requirements for both regimens were based on the formula: (resting energy expenditure × 1.5) − 2,092 kJ. The diet in both regimens had the same macronutrient and energy content. HFC was measured by proton magnetic resonance spectroscopy. Insulin sensitivity was measured by isoglycaemic–hyperinsulinaemic clamp and calculated by mathematical modelling as oral glucose insulin sensitivity (OGIS). Beta cell function was assessed during standard meal tests by C-peptide deconvolution and was quantified with a mathematical model. For statistical analysis, 2 × 2 crossover ANOVA was used.ResultsThe intention-to-treat analysis included all participants (n = 54). Body weight decreased in both regimens (p < 0.001), more for B2 (−2.3 kg; 95% CI −2.7, −2.0 kg for A6 vs −3.7 kg; 95% CI −4.1, −3.4 kg for B2; p < 0.001). HFC decreased in response to both regimens (p < 0.001), more for B2 (−0.03%; 95% CI −0.033%, −0.027% for A6 vs −0.04%; 95% CI −0.041%, −0.035% for B2; p = 0.009). Fasting plasma glucose and C-peptide levels decreased in both regimens (p < 0.001), more for B2 (p = 0.004 and p = 0.04, respectively). Fasting plasma glucagon decreased with the B2 regimen (p < 0.001), whereas it increased (p = 0.04) for the A6 regimen (p < 0.001). OGIS increased in both regimens (p < 0.01), more for B2 (p = 0.01). No adverse events were observed for either regimen.Conclusions/interpretationEating only breakfast and lunch reduced body weight, HFC, fasting plasma glucose, C-peptide and glucagon, and increased OGIS, more than the same caloric restriction split into six meals. These results suggest that, for type 2 diabetic patients on a hypoenergetic diet, eating larger breakfasts and lunches may be more beneficial than six smaller meals during the day.Trial registration ClinicalTrials.gov number, NCT01277471, completed.Funding Grant NT/11238-4 from Ministry of Health, Prague, Czech Republic and the Agency of Charles University – GAUK No 702312.

Major controversy exists as to whether increased C-reactive protein (CRP) contributes to individual components of the metabolic syndrome or is just a secondary response to inflammatory disease processes. We measured blood pressure and metabolic phenotypes in spontaneously hypertensive rats (SHR) in which we transgenically expressed human CRP in liver under control of the apoE promoter. In SHR transgenic rats, serum levels of human CRP approximated the endogenous levels of CRP normally found in the rat. Systolic and diastolic blood pressures measured by telemetry were 10–15 mmHg greater in transgenic SHR expressing human CRP than in SHR controls (P<0.01). During oral glucose tolerance testing, transgenic SHR exhibited hyperinsulinemia compared to controls (insulin area under the curve 36±7 versus 8±2 nmol/L/2h, respectively, P<0.05). Transgenic SHR also exhibited resistance to insulin stimulated glycogenesis in skeletal muscle (174±18 versus 278±32 nmol glucose/g/2h, P<0.05), hypertriglyceridemia (0.84±0.05 versus 0.64±0.03 mmol/L, P<0.05), reduced serum adiponectin (2.4±0.3 versus 4.3±0.6 mmol/L, P<0.05), and microalbuminuria (200±35 versus 26±5 mg albumin/g creatinine, respectively, P<0.001). Transgenic SHR had evidence of inflammation and oxidative tissue damage with increased serum levels of interleukin 6 (IL6) (36.4±5.2 versus 18±1.7 pg/ml, P<0.005) and increased hepatic and renal TBARS (1.2±0.09 versus 0.8±0.07 and 1.5±0.1 versus 1.1±0.05 nM/mg protein, respectively, P<0.01), suggesting that oxidative stress may be mediating adverse effects of increased human CRP. These findings are consistent with the hypothesis that increased CRP is more than just a marker of inflammation and can directly promote multiple features of the metabolic syndrome.

Recently, the relationship of mitochondrial DNA (mtDNA) variants to metabolic risk factors for diabetes and other common diseases has begun to attract increasing attention. However, progress in this area has been limited because (1) the phenotypic effects of variation in the mitochondrial genome are difficult to isolate owing to confounding variation in the nuclear genome, imprinting phenomena, and environmental factors; and (2) few animal models have been available for directly investigating the effects of mtDNA variants on complex metabolic phenotypes in vivo. Substitution of different mitochondrial genomes on the same nuclear genetic background in conplastic strains provides a way to unambiguously isolate effects of the mitochondrial genome on complex traits. Here we show that conplastic strains of rats with identical nuclear genomes but divergent mitochondrial genomes that encode amino acid differences in proteins of oxidative phosphorylation exhibit differences in major metabolic risk factors for type 2 diabetes. These results (1) provide the first direct evidence linking naturally occurring variation in the mitochondrial genome, independent of variation in the nuclear genome and other confounding factors, to inherited variation in known risk factors for type 2 diabetes; and (2) establish that spontaneous variation in the mitochondrial genome per se can promote systemic metabolic disturbances relevant to the pathogenesis of common diseases.[Supplemental material is available online at www.genome.org.]Recently, the potential role of the mitochondrial genome in the pathogenesis of type 2 diabetes and other common diseases has begun to attract increasing attention (Wallace 2005). Mitochondrial DNA is exclusively of maternal origin, and some studies have indicated that the inheritance of type 2 diabetes may be biased toward the maternal lineage (Alcolado et al. 2002). Sun et al. (2003) have estimated that mitochondrial DNA mutations might be involved in >20% of cases of type 2 diabetes. In addition, Wilson et al. (2004) have identified a homoplasmic mitochondrial DNA variant associated with the maternal transmission of hypercholesterolemia, hypomagnesemia, and hypertension through four generations of a large, carefully analyzed kindred. Rare forms of maternally transmitted diabetes associated with heteroplasmic mitochondrial DNA variants have also been reported (Mathews and Berdanier 1998;Maassen et al. 2005). These observations provide indirect evidence that sequence variation in the mitochondrial genome might contribute to inherited variation in the risk for type 2 diabetes and related metabolic disorders.Notwithstanding recent advances in mitochondrial genome research, multiple confounding factors have made it difficult to unequivocally establish a role for mitochondrial DNA variation in the regulation of risk factors for diabetes or other complex metabolic phenotypes. For example, effects of maternal environment or imprinting may contribute to matrilineal transmission patterns of the phenotypes of interest....