SPINA-GR

Key takeaways

SPINA-GR belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SPINA-GR to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SPINA-GR from memory before moving on to harder problems.

Reference excerpt

SPINA-GR is a calculated biomarker for insulin sensitivity. It represents insulin receptor gain. The method of calculation is based on a time-discrete nonlinear feedback model of insulin-glucose homeostasis that is rooted in the MiMe-NoCoDI modeling platform for endocrine systems.

How to determine GR The index is derived from a mathematical model of insulin-glucose homeostasis that incorporates fundamental physiological motifs. For diagnostic purposes, it is calculated from fasting insulin and glucose concentrations with:

G ^ R = G 1 P ( ∞ ) ( D R + [ I ] ( ∞ ) ) G E [ I ] ( ∞ ) [ G ] ( ∞ ) − D R G E [ I ] ( ∞ ) − 1 G E {\displaystyle {\widehat {G}}_{R}={\frac {{G}_{1}P(\infty )({D}_{R}+\left[I\right](\infty ))}{{G}_{E}\left[I\right](\infty )[G](\infty )}}-{\frac {{D}_{R}}{{G}_{E}[I](\infty )}}-{\frac {1}{{G}_{E}}}} . [I](∞): Fasting Insulin plasma concentration (mol/L) [G](∞): Fasting blood glucose concentration (mol/L) G1: Parameter for pharmacokinetics (154.93 s/L) DR: EC50 of insulin at its receptor (1,6 nmol/L) GE: Effector gain (50 s/mol) P(∞): Constitutive endogenous glucose production (150 μmol/s)

Clinical significance

Validity Compared to healthy volunteers, SPINA-GR is significantly reduced in persons with prediabetes and diabetes mellitus, and it correlates with the M value in glucose clamp studies, triceps skinfold, subscapular skinfold and (better than HOMA-IR and QUICKI) with the two-hour value in oral glucose tolerance testing (OGTT), glucose rise in OGTT, waist-to-hip ratio, body fat content (measured via DXA) and the HbA1c fraction.

Clinical utility Both in the FAST study, an observational case-control sequencing study including 300 persons from Germany, and in a large sample from the NHANES study, SPINA-GR differed more clearly between subjects with and without diabetes than the corresponding HOMA-IR, HOMA-IS and QUICKI indices.

Scientific implications and other uses Together with the secretory capacity of pancreatic beta cells (SPINA-GBeta), SPINA-GR provides the foundation for the definition of a fasting based disposition index of insulin-glucose homeostasis (SPINA-DI). In combination with SPINA-GBeta and whole-exome sequencing, calculating SPINA-GR helped to identify a new form of monogenetic diabetes (MODY) that is characterised by primary insulin resistance and results from a missense variant of the type 2 ryanodine receptor (RyR2) gene (p.N2291D).

Pathophysiological implications In lean subjects it is significantly higher than in a population with obese persons. In several populations, SPINA-GR correlated with the area under the glucose curve and 2-hour concentrations of glucose, insulin and proinsulin in oral glucose tolerance testing, concentrations of free fatty acids, ghrelin and adiponectin, and the HbA1c fraction. SPINA-GR declines with increasing adherence to mediterranean diet, which may be explained by increased use of other macronutrients for energy production. In hidradenitis suppurativa, an inflammatory skin disease, SPINA-GR is reduced. If this state is uncompensated by increased beta-cell function the static disposition index (SPINA-DI) is reduced, resulting in the onset of diabetes mellitus.

Predictive aspects In a longitudinal evaluation of the NHANES study, a large sample of the general US population, over 10 years, reduced SPINA-DI, calculated as the product of SPINA-GBeta times SPINA-GR, significantly predicted all-cause mortality.

See also SPINA-GBeta SPINA-GD SPINA-GT Homeostatic model assessment QUICKI

Notes

References

External links Software for calculating SPINA-GBeta and other parameters for endotyping glucose homeostasis. (Permanent DOI), (General information and US mirror) Functions for R and S for calculating SPINA-GBeta, SPINA-GR and SPINA-DI. (Permanent DOI)

Worked examples

Example 1 — a first encounter with SPINA-GR

Start with the simplest possible case. Write down what SPINA-GR claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SPINA-GR before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SPINA-GR ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SPINA-GR

In research: SPINA-GR appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SPINA-GR in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SPINA-GR is common in secondary-school and first-year university syllabi. It links to neighbouring topics Diabetes, Endocrine procedures, Endocrinology, so understanding it makes those chapters shorter.
In everyday life: Look for SPINA-GR outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study SPINA-GR in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SPINA-GR means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SPINA-GR out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SPINA-GR in simple terms?

SPINA-GR is a calculated biomarker for insulin sensitivity. It represents insulin receptor gain.

Why does SPINA-GR matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SPINA-GR?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SPINA-GR.