雅思阅读 143: Insulin Resistance — The Silent Precursor（胰岛素抵抗：沉默的前奏曲）

改编自 NCBI Bookshelf / StatPearls "Insulin Resistance"（2023年更新）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.ncbi.nlm.nih.gov/books/NBK507839/

Reading Passage

A. Type 2 diabetes is commonly imagined as a disease of the pancreas — an organ that, having exhausted its ability to manufacture insulin, leaves blood sugar unregulated. The reality behind the illness is more subtle and far better known to physiologists than to the public. Long before any diagnosis is made, the body's tissues quietly stop heeding the hormone they once obeyed, a state known as insulin resistance. By the time blood sugar finally crosses the threshold into diabetes, this underlying resistance has usually been building for a decade or more. Clinicians estimate that the condition precedes the clinical disease by roughly ten to fifteen years, meaning that the disorder which appears abruptly in middle age is, in metabolic terms, neither sudden nor entirely unpredictable. What makes it particularly costly is that it rarely announces itself. The chemistry drifts, often without symptoms, until the output of the pancreas can no longer conceal the problem. Understanding how a healthy cell gradually becomes deaf to insulin is therefore the key to understanding an illness that now affects hundreds of millions of people around the world. Yet for all its scale, the condition is usually discussed only after it has declared itself as something else — a heart attack, a fatty liver, or a high reading on a blood-pressure machine.

B. Three organs bear the burden. Skeletal muscle alone absorbs up to seventy percent of the glucose cleared from the bloodstream after a meal, so it is the first place resistance shows. When calories are chronically excessive, muscle fibres accumulate a form of fat called diacylglycerol, which switches on an enzyme that dampens insulin's signal. The result is that the cell no longer moves its glucose transporter to the surface, and sugar that ought to be consumed in muscle is redirected elsewhere. The liver, the body's chemical refinery, is next. Faced with the same flood of surplus fuel — again sensed as diacylglycerol — it switches on a related enzyme of its own and, paradoxically, keeps pouring out glucose even when insulin instructs it to stop. The third tissue, fat, fails to hold onto its stores, releasing free fatty acids into the circulation that aggravate both liver and muscle. None of these defects is dramatic in isolation; together, however, they constitute a coordinated shutdown of the body's normal response to food. No single tissue, in other words, fails on its own; each amplifies the strain on the others, so that what begins as a simple surplus of fuel ends as a system-wide deafness to the very hormone meant to handle it.

C. The body does not surrender without a fight. Initially the pancreas compensates, pumping out extra insulin to force the resistant tissues to open their doors. This compensatory flood, termed hyperinsulinaemia, can hold fasting sugar near the normal range for years, and it is largely why the disease hides for so long. Yet the compensation is itself part of the problem: high circulating insulin promotes further fat storage and may, over time, worsen the very resistance it is meant to overcome. Only when the insulin-producing beta cells can no longer keep pace with the demand does fasting glucose begin to climb. Once that mismatch becomes chronic, levels settle into the range doctors label diabetes. Weight gain, usually attributed simply to overeating, tends to accompany this phase, though the relationship between excess insulin and expanding waistlines is less direct than it appears, because the hormone's appetite for building tissue weakens as resistance deepens. Clinicians sometimes mistake the rising insulin levels themselves for a reassuring sign, when in fact they are the body straining against a wall it is no longer quite tall enough to climb.

D. Detecting resistance, however, is harder than describing it. There is no single, universally accepted blood test for the condition; in practice clinicians infer it from a cluster of accompanying signs — raised triglycerides, lowered protective cholesterol, elevated blood pressure — that together make up what is called metabolic syndrome. The research gold standard, a cumbersome procedure in which insulin is infused continuously while glucose is closely monitored, is far too elaborate for routine outpatient clinics. Instead, physicians rely on simpler substitutes calculated from fasting glucose and insulin, or on ratios derived from blood lipids. These proxies are convenient but imperfect: a ratio that reliably flags resistance in one population may not hold in another, and none captures the whole picture. The absence of a straightforward diagnostic is one reason the disease is often recognised late, after complications to blood vessels, kidneys and eyes have already begun to develop. This delayed recognition is doubly unfortunate, because the earliest stages are precisely the ones that respond best to simple changes in diet and exercise, before any permanent damage has had time to set in.

E. Treatment, when it comes, begins not with a tablet but with a change of habits. Cutting calories, avoiding the rapidly digested carbohydrates that demand sudden surges of insulin, and increasing physical exercise all improve the muscle's sensitivity directly, and they remain the cornerstone of care. Drugs have their place — some lower circulating sugar, others restrain the liver's overproduction — but none substitutes for the body's own recovery of responsiveness. What the mechanistic picture ultimately suggests is that type 2 diabetes is best understood not as a failure of insulin alone but as a multi-organ response to chronic energy excess, in which muscle, liver and fat gradually forget how to use a hormone they once needed. The decade-long lag between the first silent changes and the final diagnosis is, on this view, both the disease's greatest danger and its greatest opportunity: a window in which simple, early adjustments could prevent the illness before it is ever named. Whether societies choose to use that window is another matter, for resistance gives its host no symptom to announce that a decision is being made in the body's silence.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. A three-organ response to surplus fuel ii. Why a single blood test is unreliable iii. The pancreas's compensatory response — and its limits iv. Treating diabetes with regular insulin injections v. Reversing the earliest changes through lifestyle vi. The historical discovery of insulin vii. Why glucose levels naturally rise after a meal

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. According to the passage, insulin resistance usually precedes type 2 diabetes by A. one to two years. B. roughly ten to fifteen years. C. twenty to twenty-five years. D. less than six months.

6. What happens in skeletal muscle when calories are chronically excessive? A. It stops producing insulin entirely. B. It accumulates diacylglycerol and takes up less glucose. C. It converts all glucose into glycogen. D. It becomes more sensitive to insulin.

7. Why does the condition often remain hidden for years? A. Symptoms appear only in young children. B. The pancreas compensates by secreting extra insulin. C. Doctors generally refuse to screen for it. D. Blood sugar is measured only inside hospitals.

8. What does the writer identify as the cornerstone of treatment? A. lifelong insulin injections B. expensive surgical operations C. changes to diet and physical activity D. genetic screening

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Type 2 diabetes is caused entirely by the pancreas failing to produce insulin.
10. Skeletal muscle absorbs up to seventy percent of the glucose cleared from the blood after a meal.
11. The gold-standard measurement technique is routinely used in ordinary clinics.
12. The disease typically begins to damage the kidneys within the first year of resistance.
13. Raised triglycerides are one of the signs clinicians look for when inferring the condition.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The pancreas initially compensates by secreting extra insulin, producing a state known as (14) _____________ that keeps fasting sugar near normal for years. When the (15) _____________ cells can no longer meet demand, blood glucose climbs into the diabetic range.

答案与解析

← 上一篇 | 返回雅思焦点 | 下一篇 →