The impact of prior exposure to hypoglycaemia on the inflammatory response to a subsequent hypoglycaemic episode

BACKGROUND

Hypoglycaemia has been shown to induce a systemic pro-inflammatory response, which may be driven, in part, by the adrenaline response. Prior exposure to hypoglycaemia attenuates counterregulatory hormone responses to subsequent hypoglycaemia, but whether this effect can be extrapolated to the pro-inflammatory response is unclear. Therefore, we investigated the effect of antecedent hypoglycaemia on inflammatory responses to subsequent hypoglycaemia in humans.

METHODS

Healthy participants (n = 32) were recruited and randomised to two 2-h episodes of either hypoglycaemia or normoglycaemia on day 1, followed by a hyperinsulinaemic hypoglycaemic (2.8 ± 0.1 mmol/L) glucose clamp on day 2. During normoglycaemia and hypoglycaemia, and after 24 h, 72 h and 1 week, blood was drawn to determine circulating immune cell composition, phenotype and function, and 93 circulating inflammatory proteins including hs-CRP.

RESULTS

In the group undergoing antecedent hypoglycaemia, the adrenaline response to next-day hypoglycaemia was lower compared to the control group (1.45 ± 1.24 vs 2.68 ± 1.41 nmol/l). In both groups, day 2 hypoglycaemia increased absolute numbers of circulating immune cells, of which lymphocytes and monocytes remained elevated for the whole week. Also, the proportion of pro-inflammatory CD16+-monocytes increased during hypoglycaemia. After ex vivo stimulation, monocytes released more TNF-α and IL-1β, and less IL-10 in response to hypoglycaemia, whereas levels of 19 circulating inflammatory proteins, including hs-CRP, increased for up to 1 week after the hypoglycaemic event. Most of the inflammatory responses were similar in the two groups, except the persistent pro-inflammatory protein changes were partly blunted in the group exposed to antecedent hypoglycaemia. We did not find a correlation between the adrenaline response and the inflammatory responses during hypoglycaemia.

CONCLUSION

Hypoglycaemia induces an acute and persistent pro-inflammatory response at multiple levels that occurs largely, but not completely, independent of prior exposure to hypoglycaemia. Clinical Trial information Clinicaltrials.gov no. NCT03976271 (registered 5 June 2019).

Primary hyperparathyroidism in young patients is associated with metabolic disorders: a prospective comparative study

BACKGROUND

Components of metabolic syndrome can be observed in patients with primary hyperparathyroidism (PHPT). The link between these disorders remains unclear due to the lack of relevant experimental models and the heterogeneity of examined groups. The effect of surgery on metabolic abnormalities is also controversial. We conducted a comprehensive assessment of metabolic parameters in young patients with PHPT.

METHODS

One-center prospective comparative study was carried out. The participants underwent a complex biochemical and hormonal examination, a hyperinsulinemic euglycemic and hyperglycemic clamps, a bioelectrical impedance analysis of the body composition before and 13 months after parathyroidectomy compared to sex-, age- and body mass index matched healthy volunteers.

RESULTS

45.8% of patients (n = 24) had excessive visceral fat. Insulin resistance was detected in 54.2% of cases. PHPT patients had higher serum triglycerides, lower M-value and higher C-peptide and insulin levels in both phases of insulin secretion compared to the control group (p < 0.05 for all parameters). There were tendencies to decreased fasting glucose (p = 0.031), uric acid (p = 0.044) and insulin levels of the second secretion phase (p = 0.039) after surgery, but no statistically significant changes of lipid profile and M-value as well as body composition were revealed. We obtained negative correlations between percent body fat and osteocalcin and magnesium levels in patients before surgery.

CONCLUSION

PHPT is associated with insulin resistance that is the main risk factor of serious metabolic disorders. Surgery may potentially improve carbohydrate and purine metabolism.

Fetuin-A mediates the difference in adipose tissue insulin resistance between young adult pakistani and norwegian patients with type 2 diabetes

BACKGROUND

South-Asian immigrants to Western countries have a high prevalence of type 2 diabetes mellitus (T2DM) and increased adipose tissue insulin resistance (AT-IR), as compared to their Western counterparts. Fetuin-A is a hepatokine known to influence AT-IR.

AIM

Can plasma fetuin-A concentrations explain an ethnic difference in adipose tissue insulin resistance?

METHODS

We performed a two-step euglycemic-hyperinsulinaemic clamp and measured plasma concentrations of fetuin-A and non-esterified fatty acids (NEFA), in 18 Pakistani and 21 Norwegians with T2DM (age 29-45y) in Norway. AT-IR was calculated as NEFA-suppression during the clamp. The adipokines/cytokines leptin, adiponectin, visfatin, PTX3, IL-1β, INF-γ, and IL-4 were measured in fasting plasma. Liver fat was estimated by CT-scans.

RESULTS

Despite a lower BMI, Pakistani patients displayed higher AT-IR than Norwegians. NEFA-suppression during clamp was lower in Pakistani than Norwegians (mean=-20.6%, 95%CI=[-40.8, -0.01] and p = 0.046). Plasma fetuin-A concentration was higher in Pakistani than Norwegians (43.4 ng/mL[12.7,74.0], p = 0.007) and correlated negatively to %NEFA-suppression during clamp (rho=-0.39, p = 0.039). Plasma fetuin-A concentration explained 22% of the ethnic difference in NEFA-suppression during the clamp. Pakistani patients exhibited higher plasma leptin and lower PTX3 levels than Norwegian, and plasma visfatin correlated positively to plasma fetuin-A levels in the Pakistani patients. We observed no correlation between plasma fetuin-A and liver fat, but fetuin-A correlated negatively with plasma IL-1β, INF-γ, and IL-4 concentrations. Plasma IL-4 concentration was lower in Pakistani than in Norwegian patients.

CONCLUSION

Fetuin-A may contribute to explain the discrepancy in T2DM prevalence between Pakistani and Norwegians patients by influencing AT-IR.

Twenty-four hour assessments of substrate oxidation reveal differences in metabolic flexibility in type 2 diabetes that are improved with aerobic training

AIMS/HYPOTHESIS

The aim of this study was to assess metabolic flexibility (MetFlex) in participants with type 2 diabetes within the physiologically relevant conditions of sleeping, the post-absorptive (fasting) state and during meals using 24 h whole-room indirect calorimetry (WRIC) and to determine the impact of aerobic training on these novel features of MetFlex.

METHODS

Normal-weight, active healthy individuals (active; n = 9), obese individuals without type 2 diabetes (ND; n = 9) and obese individuals with type 2 diabetes (n = 23) completed baseline metabolic assessments. The type 2 diabetes group underwent a 10 week supervised aerobic training intervention and repeated the metabolic assessments. MetFlex was assessed by indirect calorimetry in response to insulin infusion and during a 24 h period in a whole-room indirect calorimeter. Indices of MetFlex evaluated by WRIC included mean RQ and RQ kinetic responses after ingesting a standard high-carbohydrate breakfast (RQ_BF) and sleep RQ (RQ_sleep). Muscle mitochondrial energetics were assessed in the vastus lateralis muscle in vivo and ex vivo using ³¹P-magnetic resonance spectroscopy and high-resolution respirometry, respectively.

RESULTS

The three groups had significantly different RQ_sleep values (active 0.823 ± 0.04, ND 0.860 ± 0.01, type 2 diabetes 0.842 ± 0.03; p < 0.05). The active group had significantly faster RQ_BF and more stable RQ_sleep responses than the ND and type 2 diabetes groups, as demonstrated by steeper and flatter slopes, respectively. Following the training intervention, the type 2 diabetes group displayed significantly increased RQ_BF slope. Several indices of RQ kinetics had significant associations with in vivo and ex vivo muscle mitochondrial capacities.

CONCLUSIONS/INTERPRETATION

Twenty-four hour WRIC revealed that physiological RQ responses exemplify differences in MetFlex across a spectrum of metabolic health and correlated with skeletal muscle mitochondrial energetics. Defects in certain features of MetFlex were improved with aerobic training, emphasising the need to assess multiple aspects of MetFlex and disentangle insulin resistance from MetFlex in type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01911104.

FUNDING

This study was funded by the ADA (grant no. 7-13-JF-53).

Iatrogenic sciatic nerve injury secondary to clamp placement around the femoral neck during proximal femoral fracture intramedullary nailing

- 20-year-old male road-traffic accident - Sustained right acetabulum fracture, left proximal femur fracture, right patella fracture and pulmonary contusions - Had fixation within 4 days of his left proximal femur fracture and his right acetabulum:-Following fixation of his left femur fracture, developed symptoms of complete left sciatic nerve palsy.-At the time of surgery, a heygroves clamp around the neck of the femur was used to assist in the reduction of the fracture.-Subsequent exploration of the sciatic nerve showed several clamp indentations on it but fascicles in continuity. - Nerve conduction studies at 4 months post-operatively confirmed a high sciatic nerve injury. - The patient has still not recovered any function 1 year post-operatively.

Investigating the static or dynamic flexural and compressive stresses on flexible tubing: Comparison of clamp and peristaltic pump impact on surface damages and particles leaching during infusion acts

This paper deals with the impact of the mechanical stresses on plasticized PVC infusion tubing. Stresses due to clamping were compared to those due to the use of a peristaltic pump. The degradation of the inner surface of plastic tubing due to a dynamic load with repeated flexion and compression was extensively studied in the case of peristaltic pump stress during extracorporeal (EC) acts. Even if clamping results in a less repeated stress, we show it can also lead to damages on the inner lumen of the tubing, especially in static conditions. As these degradations were responsible of particle shedding in the case of EC processes, a first evaluation of particular contamination was performed on the stressed infusion tubes.

Acute hyperglycaemia does not have a consistent adverse effect on exercise performance in recreationally active young people with type 1 diabetes: a randomised crossover in-clinic study

AIMS/HYPOTHESIS

In individuals with type 1 diabetes, chronic hyperglycaemia impairs aerobic fitness. However, the effect of acute marked hyperglycaemia on aerobic fitness is unclear, and the impact of insulin level has not been examined. In this study, we explored if acute hyperglycaemia with higher or low insulin levels affects [Formula: see text] and other exercise performance indicators in individuals with type 1 diabetes.

METHODS

Eligible participants were aged 14 to 30 years, with complication-free, type 1 diabetes and HbA_1c ≤ 75 mmol/mol (≤9%). Participants exercised in a clinical laboratory under three clamp (constant insulin, variable glucose infusion) conditions: euglycaemia (5 mmol/l) with 20 mU [m² BSA]^-1 min^-1 insulin (where BSA is body surface area) (Eu20); hyperglycaemia (17 mmol/l) with 20 mU [m² BSA]^-1 min^-1 insulin (Hyper20); and hyperglycaemia (17 mmol/l) with 5 mU [m² BSA]^-1 min^-1 insulin (Hyper5) on separate days. Participants and the single testing assessor were blinded to condition, with participants allocated to randomised testing condition sequences as they were consecutively recruited. Standardised testing (in order) conducted on each of the three study days included: triplicate 6 second sprint cycling, grip strength, single leg static balance, vertical jump and modified Star Excursion Balance Test, ten simple and choice reaction times and one cycle ergometer [Formula: see text] test. The difference between conditions in the aforementioned testing measures was analysed, with the primary outcome being the difference in [Formula: see text].

RESULTS

Twelve recreationally active individuals with type 1 diabetes (8 male, mean ± SD 17.9 ± 3.9 years, HbA_1c 61 ± 11 mmol/mol [7.7 ± 1.0%], 7 ± 3 h exercise/week) were analysed. Compared with Eu20, [Formula: see text] was lower in Hyper20 (difference 0.17 l/min [95% CI 0.31, 0.04; p = 0.02] 6.6% of mean Eu20 level), but Hyper5 was not different (p = 0.39). Compared with Eu20, sprint cycling peak power was not different in Hyper20 (p = 0.20), but was higher in Hyper5 (64 W [95% CI 13, 115; p = 0.02] 13.1%). Hyper20 reaction times were not different (simple: p = 0.12) but Hyper5 reaction times were slower (simple: 11 milliseconds [95% CI 1, 22; p = 0.04] 4.7%) than Eu20. No differences between Eu20 and either hyperglycaemic condition were observed for the other testing measures (p > 0.05).

CONCLUSIONS/INTERPRETATION

Acute marked hyperglycaemia in the higher but not low insulin state impaired [Formula: see text] but to a small extent. Acute hyperglycaemia had an insulin-dependent effect on sprint cycling absolute power output and reaction time but with differing directionality (positive for sprint cycling and negative for reaction time) and no effect on the other indicators of exercise performance examined. We find that acute hyperglycaemia is not consistently adverse and does not impair overall exercise performance to an extent clinically relevant for recreationally active individuals with type 1 diabetes.

FUNDING

This research was funded by Diabetes Research Western Australia and Australasian Paediatric Endocrine Group grants.

Targeted lipidomics reveals associations between serum sphingolipids and insulin sensitivity measured by the hyperinsulinemic-euglycemic clamp

AIMS

Sphingolipids(SPs) and their substrates and constituents, fatty acids (FAs), are implicated in the pathogenesis of various metabolic diseases associated. This study aimed to systematically investigate the associations between serum sphingolipids and insulin sensitivity as well as insulin secretion.

METHODS

We conducted a lipidomics evaluation of molecularly distinct SPs in the serum of 86 consecutive Chinese adults using LC/MS. The glucose infusion rate over 30 min (GIR₃₀) was measured under steady conditions to assess insulin sensitivity by the gold standard hyperinsulinemic-euglycemic clamp. We created the ROC curves to detect the serum SMs diagnostic value.

RESULTS

Total and subspecies of serum SMs and globotriaosyl ceramides (Gb3s) were positively related to GIR₃₀, free FAs (FFA 16:1, FFA20:4), some long chain GM3 and complex ceramide GluCers showed strong negative correlations with GIR₃₀. Notably, ROC curves showed that SM/Cer and SM d18:0/26:0 may be good serum lipid predictors of diagnostic indicators of insulin sensitivity close to conventional clinical indexes such as 1/HOMA-IR (areas under the curve > 0.80) based on GIR₃₀ as standard diagnostic criteria, and (SM/Cer)/(BMI*LDLc) areas under the curve = 0.93) is the best.

CONCLUSIONS

These results provide novel associations between serum sphingolipid between insulin sensitivity measured by the hyperinsulinemic-euglycemic clamp and identify two specific SPs that may represent prognostic biomarkers for insulin sensitivity.

β-cell impairment and clinically meaningful alterations in glycemia in obese youth across the glucose tolerance spectrum

BACKGROUND/AIMS

In obese youth, it is not clear what degree of β-cell impairment translates to glucose dysregulation commensurate with shifts from normal glucose tolerance (NGT) to impaired glucose tolerance (IGT) to type 2 diabetes. We aimed to investigate the quantitative relationship between β-cell (clamp-measured disposition index [DI]) and OGTT glucose area under the curve (G-AUC) in obese youth across the spectrum of glucose tolerance.

METHODS

Data from 152 youth (58 African-American [AA] and 94 American-White [AW]; 73 NGT, 48 IGT, and 31 type 2 diabetes) who completed a 3-h hyperinsulinemic (80 mu/m²/min)-euglycemic clamp, and a 2-h hyperglycemic (225 mg/dL) clamp synchronized with a 2-h OGTT were examined.

RESULTS

In IGT vs. NGT, 36% lower DI corresponded to 27% higher G-AUC; in type 2 diabetes vs. IGT, 65% lower DI related to 25% higher G-AUC, and in type 2 diabetes vs. NGT, 78% lower DI paralleled 59% higher G-AUC. Although AA vs. AW youth had larger decrements in DI, from NGT to IGT and from NGT to type 2 diabetes, they displayed comparable increments in G-AUC.

CONCLUSION

At least ~35-50% recovery in β-cell function might be needed to have clinically meaningful improvement in G-AUC commensurate with conversion to better glucose tolerance. Mechanism(s) protective against dysglycemia might be operative in AA vs. AW youth despite greater declines in DI. Treatments aiming to improve β-cell function should focus on degree of change in DI commensurate with clinically meaningful changes in glycemia, reflective of restoration of glucose tolerance.

Surface adhesive and hand-aided needle-assisted biopsy technique (SAHNA)

OBJECTIVE

We describe a novel and efficient CT biopsy technique that we have termed 'skin adhesive and hand-aided biopsy technique', shortened to the acronym SAHNA. This technique is ideal for biopsying surface osseous lesions where there is a lack of subcutaneous fat. This avoids the need for the radiologist's hand to be in close proximity to the CT scanner beam at the time of intervention.

METHODS

The SAHNA technique uses a plastic surgical forceps towel clamp to stabilise the biopsy needle just proximal to the lesion after piercing through the skin. The clamp itself is stabilised via a self-adhesive dressing which is stuck down to the skin at its shank.

RESULTS

In our institution, we have already used the SAHNA technique successfully in over 5 cases.

CONCLUSION

The SAHNA technique is a widely accessible and effective way of stabilising the CT biopsy needle in technically challenging superficial bony lesions.

Posterolateral clamp placement on the pelvic brim provides optimal reduction of transtectal acetabular fractures fixed through the anterior intrapelvic approach

PURPOSE

To determine the optimal position of reduction clamps applied to reduce transtectal transverse acetabular fractures approached through the anterior intrapelvic route.

METHODS

Transtectal transverse fractures were created in sawbone hemipelvis models. Fractures were reduced and held with a large pointed reduction clamp with one tine centered on the quadrilateral plate and the other placed in one of nine various positions on the pelvic brim accessible from the anterior intrapelvic (AIP) approach. Reduction was assessed by measuring maximum gapping and step-off at the joint surface.

RESULTS

The posterolateral pelvic brim clamp position provided the most accurate reduction with the smallest articular fracture gap (mean 1.09 ± 1.05 mm) and step-off (mean 0.87 ± 1.35 mm). This clamp position, compared with the other positions as a whole, also yielded the highest proportion of perfect reductions (0 mm maximum displacement) for both step-off (83% vs 34%; RR 2.4, 95% CI 1.7-3.2) and gap (88% vs 49%; RR 1.8, 95% CI 1.4 to 2.2).

CONCLUSIONS

When clamping transtectal fractures through the AIP approach, positioning the clamp posterolaterally on the pelvic brim appears to provide the best reduction in this fracture model.

Considerations and guidelines for mouse metabolic phenotyping in diabetes research

Mice are the most commonly used species in preclinical research on the pathophysiology of metabolic diseases. Although they are extremely useful for identifying pathways, mechanisms and genes regulating glucose and energy homeostasis, the specificities of the various mouse models and methodologies used to investigate a metabolic phenotype can have a profound impact on experimental results and their interpretation. This review aims to: (1) describe the most commonly used experimental tests to assess glucose and energy homeostasis in mice; (2) provide some guidelines regarding the design, analysis and interpretation of these tests, as well as for studies using genetic models; and (3) identify important caveats and confounding factors that must be taken into account in the interpretation of findings.

Examination of short and long term complications of thermocautery, plastic clamping, and surgical circumcision techniques

Objective:

In this study, thermocautery, plastic clamping, and conventional (open surgical) circumcision techniques were compared in terms of their complications.

Methods:

Male patients who underwent circumcisions between May 2014 and May 2015 in two separate pediatric surgery clinics were retrospectively analyzed using the hospital registry system. These patients were evaluated in terms of age, accompanying pathologies, anesthesia techniques, complication rates, duration of surgery, and circumcision techniques. A statistical analysis of the data was performed, with a P<0.05 considered to be statistically significant.

Results:

The patients were divided into three groups according to the circumcision method: conventional surgical circumcision (n=833), thermocautery (n=1011), and plastic clamp (n=218). Complications were observed in 21 cases (1%): bleeding (11), infection (2), trapped penis (6), meatitis (1), and scrotal injury (1). There were significantly fewer complications in the thermocautery technique when compared to the clamping and surgical circumcision techniques. The plastic clamping and thermocautery techniques were superior to a surgical circumcision in terms of the operation time.

Conclusion:

The thermocautery circumcision technique can be used easily in both the operating theatre and in designated circumcision rooms, with a lower complication rate, when compared to plastic clamping and surgical circumcisions.

Incretin hormone receptors are required for normal beta cell development and function in female mice

The incretin hormones, glucose dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1), potentiate insulin secretion and are responsible for the majority of insulin secretion that occurs after a meal. They may also, however, have a fundamental role in pancreatic beta cell development and function, independently of their role in potentiating insulin secretion after a meal. This has led to observations that a loss of GIP or GLP-1 action affects normal beta cell function, however each one of the incretin hormones may compensate when the action of the other is lost and therefore the overall impact of the incretin hormones on beta cell function is not known. We therefore utilized a mouse line deficient in both the GLP-1 and GIP receptor genes, the double incretin receptor knockout (DIRKO), to determine the consequences of a lifelong, complete lack of incretin hormone action on beta cell function, in vivo, in intact animals. We found that DIRKO mice displayed impaired glucose tolerance and insulin secretion in response to both oral glucose and mixed meal tolerance tests compared to wild-type mice. Assessment of beta cell function using the hyperglycemic clamp technique revealed an 80% decrease in first phase insulin response in DIRKO mice, but a normal second phase insulin secretion. A similar decline was seen when wild-type mice were given acute intravenous injection of glucose together with the GLP-1 receptor antagonist Ex9-39. Ex vivo assessments of the pancreas revealed significantly fewer islets in the pancreata of DIRKO mice despite no differences in total pancreatic mass. Insulin secretion from isolated islets of DIRKO mice was impaired to a similar extent to that seen during the hyperglycemic clamp. Insulin secretion in wild-type islets was impaired by acute treatment with Ex9-39 to a similar extent as the in vivo intravenous glucose tolerance tests. In conclusion, a loss of the action of both incretin hormones results in direct impairment of beta cell function both in vivo and in vitro in a process that appears to be independent of the intestinally secreted incretin hormones. We therefore conclude that the incretin hormones together significantly impact both beta-cell function and beta-cell development.

Hyperinsulinism and polycystic ovary syndrome (PCOS): role of insulin clearance

PURPOSE

Insulin resistance and compensatory hyperinsulinism are the predominant metabolic defects in polycystic ovary syndrome (PCOS). However, hyperinsulinism, as well as being compensatory, can also express a condition of reduced insulin clearance. Our aim was to evaluate the differences in insulin action and metabolism between women with PCOS (with normal glucose tolerance) and age- and BMI-matched women with prediabetes (without hyperandrogenism and ovulatory disorders).

METHODS

22 women with PCOS and 21 age/BMI-matched women with prediabetes were subjected to a Hyperinsulinemic-euglycemic clamp and an Oral Glucose tolerance Test (OGTT). Insulin sensitivity was assessed by the glucose infusion rate during clamp (M value); insulin secretion by Insulinogenic index, Oral Disposition Index (DIo) and AUC(2h-insulin) during OGTT; and insulin clearance by the metabolic clearance rate of insulin (MCRI) during clamp.

RESULTS

Women with PCOS showed significantly higher levels of AUC(2h-insulin) (p < 0.011), Insulinogenic Index (p < 0.001), DIo (p = 0.002) and significantly lower levels of AUC(2h-glucos)e (p = 0.001). No difference was found between the two groups regarding insulin sensitivity (M value). Lower levels of MCRI were found in women with PCOS [420 (IQR 227-588) vs. 743 (IQR 597-888) ml m(-2) min(-1): p < 0.001]. Furthermore, in the PCOS group, a strong independent inverse correlation was only observed between MCRI and AUC(2h-insulin) (PCOS: β:-0.878; p < 0.001; Prediabetes: β:-0.501; p = 0.019).

CONCLUSIONS

Our study suggests that in normoglycemic women with PCOS there is peripheral insulin sensitivity similar to that of women with prediabetes. What sets PCOS apart is the hyperinsulinism, today still simplistically defined "compensatory"; actually this is mainly related to decreased insulin clearance whose specific causes and dynamics have yet to be clarified.

Multiscale evaluation of cellular adhesion alteration and cytoskeleton remodeling by magnetic bead twisting

Cellular adhesion forces depend on local biological conditions meaning that adhesion characterization must be performed while preserving cellular integrity. We presently postulate that magnetic bead twisting provides an appropriate stress, i.e., basically a clamp, for assessment in living cells of both cellular adhesion and mechanical properties of the cytoskeleton. A global dissociation rate obeying a Bell-type model was used to determine the natural dissociation rate ([Formula: see text]) and a reference stress ([Formula: see text]). These adhesion parameters were determined in parallel to the mechanical properties for a variety of biological conditions in which either adhesion or cytoskeleton was selectively weakened or strengthened by changing successively ligand concentration, actin polymerization level (by treating with cytochalasin D), level of exerted stress (by increasing magnetic torque), and cell environment (by using rigid and soft 3D matrices). On the whole, this multiscale evaluation of the cellular and molecular responses to a controlled stress reveals an evolution which is consistent with stochastic multiple bond theories and with literature results obtained with other molecular techniques. Present results confirm the validity of the proposed bead-twisting approach for its capability to probe cellular and molecular responses in a variety of biological conditions.

Posterior atlantoaxial fixation: a review of all techniques

BACKGROUND CONTEXT

Posterior atlantoaxial fixation is an effective treatment for atlantoaxial instability. Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. However, there is no article reviewing all the posterior atlantoaxial fixation techniques yet.

PURPOSE

The aim was to review the evolution and advancements of posterior atlantoaxial fixation.

STUDY DESIGN

This was a literature review.

METHODS

The application of all posterior fixation techniques in atlantoaxial stabilization, including wiring techniques, interlaminar clamp fixation, transarticular fixation, screw-plate systems, screw-rod systems, and hook-screw systems, are reviewed and discussed. Recent advancements on the novel technique of atlantoaxial fixation are described. The combination of the C1 and C2 screws in screw-rod systems are described in detail.

RESULTS

All fixation techniques are useful. The screw-rod system appears to be the most popular approach. However, many novel or modified fixation methods have been introduced in recent years.

CONCLUSIONS

Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. The wiring technique and interlaminar clamps technique have fallen out of favor because of the development of newer and superior fixation techniques. The C1-C2 transarticular screw technique may remain the gold standard for atlantoaxial fusion, whereas screw-rod systems, especially the C1 pedicle screw combined with C2 pedicle/pars screw fixation, have become the most popular fixation techniques. Hook-screw systems are alternatives for atlantoaxial fixation.

Knockout of STAT3 in skeletal muscle does not prevent high-fat diet-induced insulin resistance

Objective

Increased signal transducer and activator of transcription 3 (STAT3) signaling has been implicated in the development of skeletal muscle insulin resistance, though its contribution, in vivo, remains to be fully defined. Therefore, the aim of this study was to determine whether knockout of skeletal muscle STAT3 would prevent high-fat diet (HFD)-induced insulin resistance.

Methods

We used Cre-LoxP methodology to generate mice with muscle-specific knockout (KO) of STAT3 (mKO). Beginning at 10 weeks of age, mKO mice and their wildtype/floxed (WT) littermates either continued consuming a low fat, control diet (CON; 10% of calories from fat) or were switched to a HFD (60% of calories from fat) for 20 days. We measured body composition, energy expenditure, oral glucose tolerance and in vivo insulin action using hyperinsulinemic-euglycemic clamps. We also measured insulin sensitivity in isolated soleus and extensor digitorum longus muscles using the 2-deoxy-glucose (2DOG) uptake technique.

Results

STAT3 protein expression was reduced ∼75–100% in muscle from mKO vs. WT mice. Fat mass and body fat percentage did not differ between WT and mKO mice on CON and were increased equally by HFD. There were also no genotype differences in energy expenditure or whole-body fat oxidation. As determined, in vivo (hyperinsulinemic-euglycemic clamps) and ex vivo (2DOG uptake), skeletal muscle insulin sensitivity did not differ between CON-fed mice, and was impaired similarly by HFD.

Conclusions

These results demonstrate that STAT3 activation does not underlie the development of HFD-induced skeletal muscle insulin resistance.

•

Loss of STAT3 in skeletal muscle does not effect whole body energy expenditure in mice.

•

Mice with knockout of STAT3 in skeletal muscle (mKO) develop glucose intolerance with HFD feeding similar to littermate controls.

•

HFD-induced insulin resistance in skeletal muscle is not prevented by knockout of STAT3.

High fat diet-induced modifications in membrane lipid and mitochondrial-membrane protein signatures precede the development of hepatic insulin resistance in mice

Objective

Excess lipid intake has been implicated in the pathophysiology of hepatosteatosis and hepatic insulin resistance. Lipids constitute approximately 50% of the cell membrane mass, define membrane properties, and create microenvironments for membrane-proteins. In this study we aimed to resolve temporal alterations in membrane metabolite and protein signatures during high-fat diet (HF)-mediated development of hepatic insulin resistance.

Methods

We induced hepatosteatosis by feeding C3HeB/FeJ male mice an HF enriched with long-chain polyunsaturated C18:2n6 fatty acids for 7, 14, or 21 days. Longitudinal changes in hepatic insulin sensitivity were assessed via the euglycemic-hyperinsulinemic clamp, in membrane lipids via t-metabolomics- and membrane proteins via quantitative proteomics-analyses, and in hepatocyte morphology via electron microscopy. Data were compared to those of age- and litter-matched controls maintained on a low-fat diet.

Results

Excess long-chain polyunsaturated C18:2n6 intake for 7 days did not compromise hepatic insulin sensitivity, however, induced hepatosteatosis and modified major membrane lipid constituent signatures in liver, e.g. increased total unsaturated, long-chain fatty acid-containing acyl-carnitine or membrane-associated diacylglycerol moieties and decreased total short-chain acyl-carnitines, glycerophosphocholines, lysophosphatidylcholines, or sphingolipids. Hepatic insulin sensitivity tended to decrease within 14 days HF-exposure. Overt hepatic insulin resistance developed until day 21 of HF-intervention and was accompanied by morphological mitochondrial abnormalities and indications for oxidative stress in liver. HF-feeding progressively decreased the abundance of protein-components of all mitochondrial respiratory chain complexes, inner and outer mitochondrial membrane substrate transporters independent from the hepatocellular mitochondrial volume in liver.

Conclusions

We assume HF-induced modifications in membrane lipid- and protein-signatures prior to and during changes in hepatic insulin action in liver alter membrane properties – in particular those of mitochondria which are highly abundant in hepatocytes. In turn, a progressive decrease in the abundance of mitochondrial membrane proteins throughout HF-exposure likely impacts on mitochondrial energy metabolism, substrate exchange across mitochondrial membranes, contributes to oxidative stress, mitochondrial damage, and the development of insulin resistance in liver.

Toll-like receptor and pro-inflammatory cytokine expression during prolonged hyperinsulinaemia in horses: implications for laminitis

Equine laminitis, a disease of the lamellar structure of the horse's hoof, can be incited by numerous factors that include inflammatory and metabolic aetiologies. However, the role of inflammation in hyperinsulinaemic laminitis has not been adequately defined. Toll-like receptor (TLR) activation results in up-regulation of inflammatory pathways and the release of pro-inflammatory cytokines, including interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α), and may be a pathogenic factor in laminitis. The aim of this study was to determine whether TLR4 expression and subsequent pro-inflammatory cytokine production is increased in lamellae and skeletal muscle during equine hyperinsulinaemia. Standardbred horses were treated with either a prolonged, euglycaemic hyperinsulinaemic clamp (p-EHC) or a prolonged, glucose infusion (p-GI), which induced marked and moderate hyperinsulinaemia, respectively. Age-matched control horses were treated simultaneously with a balanced electrolyte solution. Treated horses developed clinical (p-EHC) or subclinical (p-GI) laminitis, whereas controls did not. Skeletal muscle and lamellar protein extracts were analysed by Western blotting for TLR4, IL-6, TNF-α and suppressor of cytokine signalling 3 (SOCS3) expression. Lamellar protein expression of TLR4 and TNF-α, but not IL-6, was increased by the p-EHC, compared to control horses. A significant positive correlation was found between lamellar TLR4 and SOCS3. Skeletal muscle protein expression of TLR4 signalling parameters did not differ between control and p-EHC-treated horses. Similarly, the p-GI did not result in up-regulation of lamellar protein expression of any parameter. The results suggest that insulin-sensitive tissues may not accurately reflect lamellar pathology during hyperinsulinaemia. While TLR4 is present in the lamellae, its activation appears unlikely to contribute significantly to the developmental pathogenesis of hyperinsulinaemic laminitis. However, inflammation may have a role to play in the later stages (e.g., repair or remodelling) of the disease.

Biomechanical evaluation of a novel posterior integrated clamp that attaches to an existing posterior instrumentation for use in thoracolumbar revision

STUDY DESIGN

An in vitro biomechanical study.

PURPOSE

To evaluate the biomechanics of a novel posterior integrated clamp (IC) that extends on an already implanted construct in comparison to single long continuous bilateral pedicle screw (BPS) and rod stabilization system.

OVERVIEW OF LITERATURE

Revision surgery in the thoracolumbar spine often necessitates further instrumentation following a failed previous back surgery. Stability of these reconstructed constructs is not known.

METHODS

Six osteoligamentous T12-L5 calf spines were tested on a spine motion simulator in the following configurations: intact, four level constructs (T13-L4), three level constructs (L1-L4), and two level constructs (L2-L4), by varying the ratio between BPS and IC. A load control protocol of 8 Nm moments was applied at a rate of 1°/sec to establish the range of motion value for each construct in flexion-extension, lateral bending, and axial rotation. Statistical analysis was performed on raw data using repeated measures analysis of variance and significance was set at p<0.05.

RESULTS

On an average, the reduction in motion for the four level continuous pedicle screw and rod construct (67%) was similar to those extended with integrated clamps (64%). Furthermore, for three level and two level constructs, no significant difference was observed between continuous pedicle screw constructs and those revised with the integrated clamps (regardless of the ratio between BPS and IC).

CONCLUSIONS

The novel posterior IC showed equivalent biomechanical rigidity to continuous pedicle screw rod constructs in revision scenarios. Clinical studies on posterior rod adjunct systems are necessary to confirm these results.